Checking access to closed subscriber group cells in a mobile network

ABSTRACT

Example disclosed mobile station methods comprise performing a first access check based on a first equivalent public land mobile network (EPLMN) list and a first registered public land mobile network (RPLMN) identifier to determine whether a mobile station is allowed to access a closed subscriber group (CSG) cell, performing a second access check based on a second EPLMN list and a second RPLMN identifier, and conditioning reporting of the CSG cell based on the first and second checks. Example disclosed network methods comprise receiving a message from a packet switched domain network node indicating whether a mobile station is allowed to access a CSG cell, and if the message indicates that the mobile station is not allowed to access the CSG cell, informing a circuit switched domain network node that a DTM handover failure has occurred.

RELATED APPLICATION(S)

This patent claims priority from U.S. Provisional Application Ser. No.61/623,977, entitled “ACCESS CHECK FOR CSG CELLS AFTER INTER-PLMNHANDOVER” and filed on Apr. 13, 2012. U.S. Provisional Application Ser.No. 61/623,977 is hereby incorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

This disclosure relates generally to mobile network and, moreparticularly, to checking access to closed subscriber group cells in amobile network.

BACKGROUND

In Universal Mobile Telecommunication System (UMTS) and Long TermEvolution (LTE) mobile networks, access to certain cells can berestricted to particular groups of users. Such a group of users isreferred to as a close subscriber group (CSG). A particular cell inwhich access is restricted to a CSG, such as a femtocell served by ahome Node-B (HNB) in a UMTS network or a home enhanced Node-B (HeNB) inan LTE network, is referred to as a CSG cell. When performing a handoverto a CSG cell, a mobile station (also referred to herein as userequipment or a UE) performs an access check involving a CSG whitelistand public land mobile network (PLMN) identification informationavailable at the mobile station to determine whether it is allowed toaccess the CSG cell. Network elements, or nodes, in the mobile network'score network also perform one or more access checks involving the CSGwhitelist and available PLMN identification information to determinewhether the mobile station is allowed to access the CSG cell. Ingeneral, the mobile station is not permitted to handover to the CSG cellunless all such access checks indicate that the mobile station isallowed to access the CSG cell.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is block diagram of an example mobile network in which access toclosed subscriber group (CSG) cells can be checked in accordance withthe examples disclosed herein.

FIG. 2 is a block diagram illustrating an example handover operation inwhich access to a CSG cell is to be checked.

FIG. 3 is a block diagram of an example mobile switching center (MSC)that can be used to implement the mobile network of FIG. 1.

FIG. 4 is a block diagram of example mobile station that can be used toimplement the mobile network of FIG. 1.

FIG. 5 is a block diagram of example base station subsystem (BSS) thatcan be used to implement the mobile network of FIG. 1.

FIG. 6 is a block diagram of example serving general packet radioservice (GPRS) support node (SGSN) that can be used to implement themobile network of FIG. 1.

FIG. 7 is a flowchart representative of an example process that may beperformed by the MSC of FIG. 3 to implement a first example approach forchecking access to CSG cells as disclosed herein.

FIG. 8 is a flowchart representative of an example process that may beperformed by the mobile station of FIG. 4 to implement a second exampleapproach for checking access to CSG cells as disclosed herein.

FIG. 9 is a flowchart representative of example processes that may beperformed by the BSS of FIG. 5 and the SGSN of FIG. 6 to implement thesecond example approach for checking access to CSG cells as disclosedherein.

FIG. 10 is a flowchart representative of an example process that may beperformed by the mobile station of FIG. 4 to implement a third exampleapproach for checking access to CSG cells as disclosed herein.

FIG. 11 is a flowchart representative of example processes that may beperformed by the BSS of FIG. 5 and the MSC of FIG. 3 to implement thethird example approach for checking access to CSG cells as disclosedherein.

FIG. 12 is a flowchart representative of example processes that may beperformed by the BSS of FIG. 5 and the MSC of FIG. 3 to implement afourth example approach for checking access to CSG cells as disclosedherein.

FIG. 13 is a flowchart representative of an example process that may beperformed by the mobile station of FIG. 4 to implement a fifth exampleapproach for checking access to CSG cells as disclosed herein.

FIG. 14 is a flowchart representative of an example process that may beperformed by the mobile station of FIG. 4 to implement a sixth exampleapproach for checking access to CSG cells as disclosed herein.

FIG. 15 is a flowchart representative of an example process that may beperformed by the BSS of FIG. 5 to implement the sixth example approachfor checking access to CSG cells as disclosed herein.

FIG. 16 is a flowchart representative of an example process that may beperformed by the SGSN of FIG. 6 to implement a seventh example approachfor checking access to CSG cells as disclosed herein.

FIG. 17 is a flowchart representative of an example process that may beperformed by the BSS of FIG. 5 to implement the seventh example approachfor checking access to CSG cells as disclosed herein.

FIG. 18 is a flowchart representative of an example process that may beperformed by the MSC of FIG. 3 to implement the seventh example approachfor checking access to CSG cells as disclosed herein.

FIG. 19 is a block diagram of an example processing system that mayexecute example machine readable instructions used to implement some orall of the processes of FIGS. 7-17 and/or 18 to implement the MSC ofFIG. 3, the mobile station of FIG. 4, the BSS of FIG. 5, the SGSN ofFIG. 6 and/or the mobile network of FIG. 1.

Wherever possible, the same reference numbers will be used throughoutthe drawing(s) and accompanying written description to refer to the sameor like elements.

DETAILED DESCRIPTION

Example methods, apparatus and articles of manufacture (e.g., storagemedia) for checking access to closed subscriber group (CSG) cells in amobile network are disclosed herein. Disclosed example methods for amobile station to check access to CSG cells include performing a firstaccess check based on a first equivalent public land mobile network(EPLMN) list (e.g., which may be null or, in other words, empty) and afirst registered public land mobile network (RPLMN) identifier todetermine whether the mobile station (e.g., such as a mobile stationoperating in a dual transfer mode (DTM)) is allowed to access a CSGcell. The example methods also include performing a second access checkbased on a second EPLMN list (e.g., which may be null or, in otherwords, empty) and a second RPLMN identifier to determine whether themobile station is allowed to access the CSG cell. The example methodsfurther include conditioning reporting of the CSG cell (e.g., via ameasurement report) based on the first access check and the secondaccess check.

In some examples, the first EPLMN list and the first RPLMN identifierrespectively include an EPLMN list and an RPLMN identifier obtained viaa most recent packet switched domain registration procedure. Forexample, the packet switched domain registration procedure can include arouting area update procedure. In such examples, the first access checkincludes comparing a public land mobile network (PLMN) identifierassociated with the CSG cell with the first EPLMN list and the firstRPLMN identifier.

In some examples, the second EPLMN list and the second RPLMN identifierrespectively comprise an EPLMN list and an RPLMN identifier obtained viaa most recent circuit switched domain registration procedure. Forexample, the circuit switched domain registration procedure can includea location update procedure. In such examples, the second access checkincludes comparing a PLMN identifier associated with the CSG cell withthe second EPLMN list and the second RPLMN identifier. Some of theseexample methods further include storing the second EPLMN list and thesecond RPLMN identifier before obtaining the first EPLMN list and thefirst RPLMN identifier via a subsequent packet switched domainregistration procedure.

In some example methods, conditioning the reporting of the CSG cellbased on the first access check and the second access check includesreporting the CSG cell if at least one of the first access checkindicates that the mobile station is allowed to access the CSG cell orthe second access check indicates that the mobile station is allowed toaccess the CSG cell, but not reporting the CSG cell if the first accesscheck indicates that the mobile station is not allowed to access the CSGcell and the second access check indicates that the mobile station isnot allowed to access the CSG cell. In some of these example methods,information is sent to the network to identify which of the first accesscheck and the second access check indicated that the mobile station isallowed to access the CSG cell. In other example methods, conditioningthe reporting of the CSG cell based on the first access check and thesecond access check includes reporting the CSG cell if the first accesscheck indicates that the mobile station is allowed to access the CSGcell and the second access check indicates that the mobile station isallowed to access the CSG cell, but not reporting the CSG cell if atleast one of the first access check indicates that the mobile station isnot allowed to access the CSG cell or the second access check indicatesthat the mobile station is not allowed to access the CSG cell.

Disclosed example methods for a mobile network to check access to CSGcells include receiving a message from a packet switched domain networknode indicating whether a mobile station is allowed to access a targetCSG cell. The example methods further include, if the message indicatesthat the mobile station is not allowed to access the target CSG cell,informing a circuit switched domain network node that a DTM handoverfailure has occurred. Some example methods further include, if themessage indicates that the mobile station is allowed to access thetarget CSG cell, permitting the DTM handover to the target CSG cell toproceed.

In some examples, the message is received at a base station subsystem(BSS) serving the mobile station. In some examples, the packet switcheddomain network node includes a serving general packet radio service(GPRS) support node (SGSN). In some examples, the circuit switcheddomain network node includes a mobile switching center (MSC).

In some examples, the received message indicates a result of the packetswitched domain network node checking whether the mobile station isallowed to access the target CSG cell. In some examples, the receivedmessage includes a cause value indicating that the CSG cell is invalidif the mobile station is not allowed to access the target CSG cell, andinclusion of the cause value indicating that the CSG cell is invalidtakes precedence over inclusion of another valid cause value. In somesuch examples, the message indicates that the mobile station is allowedto access the target CSG cell if the cause value indicating that the CSGcell is invalid is not included in the message. In other examples, thereceived message includes a first cause value indicating that the CSGcell is invalid if the mobile station is not allowed to access thetarget CSG cell, and a second cause value indicating another valid causevalue. In some such examples, the message indicates that the mobilestation is allowed to access the target CSG cell if the first causevalue indicating that the CSG cell is invalid is not included in themessage.

In some examples, the received message is a first message, and informingthe circuit switched domain network node that the DTM handover failurehas occurred includes sending a second message to the circuit switcheddomain network node indicating that an access control failure hasoccurred. In some examples, the received message is a first message, andthe methods further include receiving a second message from the circuitswitched domain network node indicating that the mobile station isallowed to access the target CSG cell, waiting for the first message,and not permitting the DTM handover to the target CSG cell to proceed ifthe first message indicates that the mobile station is not allowed toaccess the target CSG cell.

As described in greater detail below, the foregoing example methods, aswell as the further example methods, apparatus and articles ofmanufacture disclosed herein, can be used for checking access to CSGcells in mobile networks. An example of such a mobile network 100 inwhich access to CSG cells can be checked in accordance with the examplesdisclosed herein is illustrated in FIG. 1. The mobile network 100 of theillustrated example includes an example mobile device 105 (also referredto as example user equipment (UE) 105) located in a coverage areaincluding examples cells 110, 115 and 120 (also labeled as cells A, Band C, respectively, in FIG. 1). In the illustrated example, cell C(120) is a CSG cell, cell A (110) is a macro cell associated with afirst public land mobile network (PLMN), and cell B (115) is a macrocell associated with a second PLMN. The first PLMN and the second PLMNmay be associated with the same or different network operators, serviceproviders, etc. Furthermore, although two macro cells 110/115 and oneCSG cell 120 are shown in the example of FIG. 1, the mobile network 100can support any number of macro cells and/or CSG cells.

To provide radio access network (RAN) functionality, the mobile network100 of the illustrated example includes example base station subsystems(BSSs) 135 and 140 (also labeled as BSS A and B, respectively, in FIG.1). As shown in FIG. 1, BSS A (135) supports cell A (110), and BSS B(140) supports cell B (115). To provide core network (CN) functionality,the mobile network 100 of the illustrated example further includesexample mobile switching centers (MSCs) 145 and 150 (also labeled as MSCA and B, respectively, in FIG. 1), and example serving general packetradio service (GPRS) support nodes (SGSNs) 155 and 160 (also labeled asSGSN A and B, respectively, in FIG. 1). As shown in FIG. 1, MSC A (145)and SGSN A (155) are associated with PLMN A (125), with MSC A (145)providing circuit switched (CS) domain CN functionality for BSS A (135)and SGSN A (155) providing packet switched (PS) domain CN functionalityfor BSS A (135). Similarly, MSC B (150) and SGSN B (160) are associatedwith PLMN B (130), with MSC B (150) providing CS domain CN functionalityfor BSS B (140) and SGSN B (160) providing PS domain CN functionalityfor BSS B (140). In the illustrated example, the BSSs 135/140, the MSCs145/150 and the SGSNs 155/160 are implemented to be compliant (exceptwhere such compliance conflicts with the examples disclosed herein) withThird Generation Partnership Project (3GPP) specifications, such as 3GPPglobal system for mobile communications (GSM), general packet radioservice (GPRS), enhanced GPRS (EGPRS), enhanced data rates for GSMevolution (EDGE), UMTS and/or LTE specifications, etc. Furthermore,although two BSSs 135/140, two MSCs 145/150 and two SGSNs 155/160 areshown in the example of FIG. 1, the mobile network can support anynumber of BSSs, MSCs and/or SGSNs.

The mobile station 105 of FIG. 1 can be implemented by any type ofmobile station or user endpoint equipment, such as a smartphone, amobile telephone device that is portable, a mobile telephone deviceimplementing a stationary telephone, a personal digital assistant (PDA),etc., or, for example, any other type of mobile device. Furthermore,although one mobile station 105 is illustrated in FIG. 1, the examplemobile network 100 can support any number and/or type(s) of mobilestations 105.

As mentioned above, cell C (120) in the mobile network 100 of FIG. 1 isa CSG cell. To perform a handover to CSG cell C (120), the mobilestation 105 performs an access check to determine whether the mobilestation 105 is allowed to access the CSG cell C (120). Depending on thetype of handover being performed (e.g., such as a CS domain handover, aPS domain handover or a dual transfer mode (DTM) handover), one or bothof the MSC B (150) and/or the SGSN B (160) also perform an access checkto determine whether the mobile station 105 is allowed to access the CSGcell C (120). In general, the mobile station 105 is not permitted tohandover to CSG cell C (120) unless the CSG access check performed bythe mobile station 105 and the CSG access check(s) perform by the CN(e.g., performed by the MSC 150 and/or SGSN 160) all indicate that themobile station 105 is allowed to access the CSG cell. As described ingreater detail below, in prior 3GPP-compliant second generation (2G)networks (e.g., GSM networks, GPRS networks, etc.), third generation(3G) networks (e.g., UMTS networks) and fourth (4G) networks (e.g., LTEnetworks, E-UTRAN networks, etc., where E-UTRAN means evolved UMTS radioaccess network), the mobile station CSG access check and the CN accesscheck(s) may use different information to perform their respectivechecks and, thus, may yield inconsistent results. Such inconsistent CSGaccess check results can cause unnecessary exchange of handover-relatedcommunications (such as when the mobile station's access check passes,but a CN access check fails), resulting in wasted bandwidth, wastedpower consumption, etc. In contrast, the mobile station 105, the BSSs135/140, the MSCs 145/150 and/or the SGSNs 155/160 individually and/orcollectively implement one or more example approaches disclosed aboveand in greater detail below for checking access to CSG cells (e.g., theCSG cell 120) in the mobile network 100 that can reduce or eliminate thepossibility of the mobile station access check and the CN accesscheck(s) yielding inconsistent results.

To provide context for the example approaches disclosed herein forchecking access to CSG cells (e.g., the CSG cell 120) in the mobilenetwork 100, consider the following information concerning CSG cells,CSG access checking and DTM in 3GPP-compliant networks. In3GPP-compliant mobile networks, CSG cells are provided by a home Node-B(HNB) or a home enhanced Node-B (HeNB). CSG cells restrict access toparticular groups of users, referred to as CSG groups. A CSG cell, suchas the CSG cell 120, is a cell that (1) indicates that it is a CSG cell(e.g., by way of a bit broadcast in the cell's system information) and(2) broadcasts a CSG identifier (ID) (e.g., also in the cell's systeminformation). A cell can indicate none or one CSG ID, although multiplecells may share a CSG ID. A UE, such as the mobile station 105, may besubscribed to one or more CSGs, and such subscriptions may be temporary(e.g. such as when a coffee shop allows a customer a one hour access toits CSG) or (semi)permanent.

Generally, to access communication services provided by a CSG cell, a UEmust be granted restricted access to a CSG to which the subject CSG cellbelongs. A CSG whitelist identifies CSGs to which the UE is grantedrestricted access. A CSG is identified by a CSG ID and an associatedPLMN ID (because CSG IDs are local to or, in other words, guaranteed tobe unique only within a particular PLMN). Accordingly, the CSG whitelistmay be considered as a list of <CSG ID, PLMN ID> tuples, with each <CSGID, PLMN ID> tuple identifying a CSG to which the UE is granted access.In some examples (e.g., for coding/storage efficiency), the CSGwhitelist may be represented as <PLMN ID, CSG ID#1[, CSG ID#2, . . . ]>where multiple CSG IDs are permitted in a given PLMN.

In some examples, a UE's CSG whitelist may include two different lists,such as an operator list and a user list. In such examples, any <CSG ID,PLMN ID> tuple on one or both of the lists can be considered to bewithin the CSG whitelist of the UE.

Network elements (such as MSCs 145/150 and the SGSNs 155/160 of themobile network 100) are also expected to store copies of the whitelistfor the UEs registered to them. Using these CSG whitelists, the networkelements can validate handover requests and, thus, ensure that a UE isnot handed over to a CSG cell that it is not allowed to access. Thesewhitelists may be transferred from the home subscriber server (HSS) ofeach UE to the network elements performing CSG access checking.

DTM is a mode of operation in, for example, 3GPP 2G networks (e.g.,GSM/GPRS/EDGE networks) in which a UE, such as the mobile station 105,has both a CS connection (such as a voice call) and a PS connection(such as a temporary block flow (TBF)) active simultaneously. Similardual modes of operation, in which a UE has a CS connection and a PSconnection active simultaneously, exist in other networks, such as inUTRAN networks. Accordingly, the term DTM is used generally herein tomean an operating scenario in which a CS connection and a PS connectionare active simultaneously and, thus, involves CS domain and PS domainsynchronization in the core network, unless otherwise specified. In somenetworks, such as the mobile network 100, it is possible to perform aDTM handover in which both CS and PS resources are reserved for the UEin a target cell prior to the cell change, such that serviceinterruption to both CS and PS services is minimized As such, a DTMhandover usually includes a CS handover procedure (via one or more ofMSCs) and a PS handover procedure (via one or more SGSNs) performed inparallel and coordinated by the serving (or source) BSS and the targetBSS, which may be the same or different BSSs. In some examples, when aDTM handover is being performed, the MSC performing the CS handoverprocedure may be unaware that the CS handover being performed is part ofthe DTM handover. In other words, the MSC may perform the CS handoverportion of the DTM handover as if it was a CS-only handover. Similarly,when a DTM handover is being performed, the SGSN performing the PShandover procedure may be unaware that the PS handover being performedis part of the DTM handover. In other words, the SGSN may perform the PShandover portion of the DTM handover as if it was a PS-only handover.

In some examples, when a mobile network, such as the mobile network 100,is performing a DTM handover involving a CS service and a PS service,the network may treat the ongoing CS service (e.g., likely to be voice)as having higher importance to the user than the ongoing PS service.This is because the user may tolerate service interruption to the PSservice better than interruption to the CS service. In such examples, anetwork node, such as a BSS, serving a UE undergoing a DTM handover maychoose to proceed with a CS-only handover if it is not possible toproceed with the PS handover portions of the DTM handover. The PShandover may not be possible because, for example, there are no PSresources available in the target cell, either the serving or targetcell BSS (or both) does not support DTM handover, a timeout has occurredwhile waiting for a response from the PS domain, etc.

As part of the handover process to a CSG cell, some mobile networks,such as the mobile network 100, expect a UE, such as the mobile station105, to check that it has permission to access the target CSG cell. Insome examples, the UE performs this CSG access check by comparing one ormore parameters, such as, but not limited to, the CSG ID broadcast bythe CSG cell, with the entries in its local CSG whitelist. By performinga CSG access check, the UE will not send a measurement report (which mayconsume a significant amount of measurement reporting bandwidth andinitiate handover procedures unnecessarily) or similar message to thenetwork for a target CSG cell that the UE is not permitted to access.Furthermore, the BSS (or Node-B and radio network controller (RNC), oreNB, etc.) serving the UE is not aware of the CSG cells that the UE isand is not permitted to access. Therefore, the BSS is unable to restrictthe initiation of handovers to only those CSG cells which the UE canaccess unless the UE performs a CSG access check as part of the handoverprocess.

For example, 3GPP Technical Specification (TS) 25.133 (v10.6.0)specifies that a UE is to check that a target CSG cell is a CSG membercell, which means that the UE is able to access that CSG cell, beforeproviding a measurement report for the target CSG cell (and, thus,initiating a handover to the target CSG cell). According to TS 25.133,for a UE that is in a radio resource control (RRC) connected state, aCSG member cell for a UE is a cell broadcasting an identity of theregistered PLMN (RPLMN) or equivalent PLMN (EPLMN) for the UE and forwhich a CSG whitelist of the UE includes an entry containing the cell'sCSG ID and the respective PLMN identity.

As another example, 3GPP TS 44.018 (v9.11.0) specifies that a mobilestation supporting multiple radio access technologies (RATs) andoperating in dedicated mode or DTM may report a CSG cell (e.g., as aprecursor to performing a handover) if, among other things, the mobilestation has determined that it is allowed to access the CSG cell.According to 3GPP TS 44.018, the UE can access a CSG cell if the CSG IDand the PLMN ID of the CSG cell matches one of the CSG IDs stored (withtheir associated PLMN IDs) in the UE's CSG whitelist (as defined in 3GPPTS 23.122), and the PLMN ID of the CSG cell matches the PLMN ID receivedduring a most recent registration or registration update with the CSdomain or that of an equivalent PLMN. In other words, because the CSG IDfor a CSG cell is specific to a particular PLMN, the preceding examplesinvolve a UE performing a complete access check in which the CSG IDbroadcast by the CSG cell must match a CSG ID in the UE's whitelist, andthe PLMN ID stored in the whitelist tuple for that CSG cell must alsomatch the RPLMN or an EPLMN associated with the UE, for the UE to beable to access the target CSG cell. The RPLMN and the EPLMN listassociated with the UE corresponds to the most recent RPLMN and theEPLMN list received from the network, regardless of whether theinformation was received from the CS domain or the PS domain. RPLMNs andEPLMNs are discussed in greater detail below.

As noted above, in some mobile networks, the CN node(s) involved in ahandover will also perform CSG access check(s) when a handover of a UEto a target CSG cell is being attempted. For example, in prior3GPP-compliant networks, as part of the PS handover procedure, theserving (source) SGSN will check whether the UE is permitted to accessthe target CSG cell. Similarly, in prior 3GPP-compliant networks, aspart of the CS handover procedure, the serving (source) MSC will checkwhether the UE is permitted to access the target CSG cell. In the caseof DTM handover, prior 3GPP-compliant networks require both the SGSNinvolved in the PS handover and the MSC involved in the CS handover tocheck whether the UE is permitted to access the target cell.

As noted above, because the CSG ID for a CSG cell is specific to aparticular PLMN, a CSG access check performed by either a UE or a CNnode (e.g., an SGSN and/or an MSC) may involve comparing the PLMN ID forthe CSG cell with the RPLMN and any EPLMNs associated with the UE. A UE,such as the mobile station 105, has, at any given time, a singleregistered RPLMN or no RPLMN. The RPLMN for a UE is the PLMN on whichthe UE has performed a most recent non-access stratum (NAS) registrationprocedure A UE with an RPLMN may also have a list of EPLMNs provided bythe network and with which the UE is also considered to be associated.The RPLMN and EPLMN list are updated (or confirmed) as part of asuccessful PS domain or CS domain registration procedure, such as arouting area update procedure in the PS domain or a location updateprocedure in the CS domain.

However, in 3GPP-compliant mobile networks, such as the mobile network100, no CS-domain registration procedure is possible during an ongoingCS service (e.g., such as voice call). As a result, after a CS handoveror a DTM handover, no location update procedure will occur as thelocation update procedure is in the CS domain, even if the UE haschanged location areas. (This is due to the concept of an anchor MSC andthe principle specified in 3GPP TS 24.008 that, when a mobilitymanagement (MM) connection exists, no MM specific procedure can beinitiated.) Conversely, PS-domain registration procedures, such as arouting area update procedure, can occur during an ongoing PSconnection.

The foregoing behavior means that, after a CS-only handover, the RPLMNand EPLMN list in the UE will remain unchanged regardless of the PLMN ofthe new cell (because no CS-domain registration procedure can beperformed during the CS-only handover). When the CS connectionterminates, the appropriate registration procedure (e.g., a locationupdate procedure) can be performed, causing the RPLMN and EPLMN list tobe updated appropriately. However, after a DTM or PS-only handover, theRPLMN and EPLMN list can be updated by a PS-domain routing area updateprocedure shortly after the cell change, even if the PS connection isstill ongoing. As a result, after a DTM handover, the UE's new RPLMN andEPLMN list will be known to the UE and the SGSN involved in thePS-domain handover, whereas the UE's new RPLMN and EPLMN list may not beknown to the MSC involved in the CS-domain handover (because a locationupdate procedure cannot be performed until after the CS connectionterminates). This problem of different CN nodes (e.g., an SGSN vs. anMSC) having different knowledge of the UE's RPLMN and EPLMN list canpropagate with subsequent UE handovers. Also, the CN nodes (e.g., theSGSNs and MSCs) are to pass the UE's whitelist to the new serving CNnodes after each handover to permit subsequent CSG whitelist checkingduring subsequent handover procedures.

Accordingly, in prior 3GPP-compliant mobile networks, problems can arisewhen performing CSG access checks in the UE and in the CN nodes (e.g.,the MSC and SGSN) for handover to a target CSG cell after a priorhandover has occurred. These problems arise due to at least thefollowing two aspects of CSG access checking in prior 3GPP-compliantsystems. First, after a DTM handover in which both the CS session andthe PS session are ongoing, the UE and target (or new) SGSN will havethe same knowledge of the RPLMN/EPLMN list after the handover (e.g., dueto a routing area update that can occur while PS session is ongoing).However, the target (or new) MSC will not have knowledge of theRPLMN/EPLMN list (e.g., because no CS-domain registration procedure canbe performed while the CS session is ongoing). A similar problem canarise after a CS-only handover if a PS session is established after thehandover without terminating the CS connection. Second, a 3GPP-compliantUE in DTM does not know whether any handover attempt will be for aCS-only handover or for a DTM handover as the type of handover iscontrolled by the network. If the UE was to use different CSG accesschecking procedures depending on whether the UE is involved in a CS-onlyhandover or a DTM handover, the UE may select the wrong type of accesscheck if the UE assumes it is in a DTM handover, but the networkactually performs a CS-only handover, or vice versa.

FIG. 2 depicts an example operating scenarios for the mobile network 100of FIG. 1, which illustrate examples of the problem in which MSC B (150)and SGSN B (160) have different knowledge concerning the RPLMN and EPLMNlist of the mobile station 105 when the mobile station 105 isdetermining whether to report CSG cell C (120) following an inter-PLMNDTM handover from cell A (110) to cell B (115) (e.g., which may cause ahandover to be initiated by the network 100). In the illustrated exampleof FIG. 2, the foregoing problem can occur regardless of whether cell A(110) and cell B (115) are 2G (e.g., GERAN) cells or 3G (e.g., UTRAN)cells (where GERAN means GSM/EDGE radio access network). As described ingreater detail below, the example approaches disclosed herein forchecking access to CSG cells in the mobile network 100 endeavor toenable access checking with respect to a CSG cell, such as the CSG cell120, under the assumption that CN nodes (e.g., MSC B (150) and SGSN B(160)) will also validate the access check performed by the mobilestation 120. Furthermore, in view of the example scenario of FIG. 2, theexample approaches disclosed herein for checking access to CSG cells inthe mobile network 100 attempt to avoid situations in which, forexample, the mobile station 105 detects CSG cell C (120), performs anaccess check and determines that access is allowed, but a CN node (e.g.,MSC B (150) or SGSN B (160)) subsequently determines that the CSG accesscheck fails. Such a situation can result in wasted effort (e.g., batteryconsumption, time, etc.) on the part of the mobile station 105 inevaluating the CSG cell 120 (which may also cause a temporary loss ofservice while the mobile station 105 acquires broadcast systeminformation from the CSG cell 120) and also in sending the measurementreport (which may be larger than the measurement report for a non-CSGcell and, as such, consume further wasted bandwidth).

To further motivate the example approaches disclosed herein for checkingaccess to CSG cells in the mobile network 100, consider the followingpossible consequences that may occur when prior CSG access checkingrules are used in the example of FIG. 2. In a first example scenarioillustrated by FIG. 2, assume the CSG whitelist for the mobile station105 includes the tuple <PLMN C, CSG ID 77> for CSG cell C (120), where“77” is the CSG ID of the cell 120. Furthermore, assume that CSG cell C(120) indicates (e.g., via broadcast information) that it is in PLMN C(not shown). In this example scenario, the mobile station 105 begins incell A (110), and its RPLMN is PLMN A, whereas its EPLMN list is empty.Next, the mobile station 105 enters DTM and completes a DTM handover tocell B (115), which is in PLMN B. After the handover, but before anyrouting area update is performed, the RPLMN of the mobile station 105 isstill PLMN A. Also, the CSG whitelist of the mobile station 105 ispassed in the CN to MSC B (150) and SGSN B (160). Then, when the mobilestation performs a routing area update (e.g., which is permittedalthough the PS session is still active), the RPLMN for the UE becomesPLMN B and assume that the EPLMN list provided in the update includesPLMN C. At this point in the scenario, which is depicted in the FIG. 2,SGSN B (160) knows the RPLMN and EPLMN list for the mobile station 105,whereas MSC B (150) does not (e.g., because a location update procedurecannot be performed in the CS domain while the CS session is stillactive).

Continuing with the example scenario, the mobile station 105 nextdetects CSG cell C (120) and performs a CSG access check to determinewhether: (i) the CSG cell's PLMN and CSG ID are in the whitelist; and(ii) that the CSG cell's PLMN ID corresponds to the mobile station'sRPLMN or is in the mobile station's EPLMN list. In the illustratedexample, both portions of the CSG access check pass and, thus, themobile station 105 sends a measurement report for the CSG cell 120 tothe BSS 140.

In response to receiving the measurement report, the BSS 140 initiates aDTM handover to the CSG cell 120 for the mobile station 105. This causesMSC B (150) to perform a CSG check to determine whether: (i) the CSGcell's PLMN and CSG ID are in the CSG whitelist of the mobile station105; and (ii) whether the CSG cell's PLMN ID corresponds to the mobilestation's RPLMN or is in the mobile station's EPLMN list. In theillustrated example, the first portion of the CSG access check passesbecause MSC B (150) received the mobile station's CSG whitelist from MSCA (145) due to the DTM handover. However, in the illustrated examplescenario, MSC B (150) does not know the mobile station's EPLMN list(which contains PLMN C, which is the PLMN of the CSG cell 120) and,therefore, the second portion of the CSG access check performed by MSC B(150) fails.

At substantially the same time, SGSN B (160) also performs a CSG accesscheck to determine whether: (i) the CSG cell's PLMN and CSG ID are inthe CSG whitelist of the mobile station 105; and (ii) whether the CSGcell's PLMN ID corresponds to the mobile station's RPLMN or is in themobile station's EPLMN list. In the illustrated example, the firstportion of the CSG access check passes because SGSN B (160) received themobile station's CSG whitelist from SGSN A (155) due to the DTMhandover. Furthermore, unlike the check performed by MSC B (150), thesecond portion of the access check performed by SGSN B (160) also passesbecause, due to the routing area update, SGSN B (160) knows the mobilestation's EPLMN list (which contains PLMN C, which is the PLMN of theCSG cell 120). However, when prior CSG access checking rules are used,although the SGSN's access check passes, the DTM handover to CSG cell C(120) fails because the CS portion of the handover failed due to theMSC's access check having failed.

A second example scenario which may occur in the example of FIG. 2 alsoillustrates possible consequences that may occur when prior CSG accesschecking rules are used in mobile networks. In the second examplescenario illustrated by FIG. 2, assume that the mobile station 105initially is operating in CS-only mode or in DTM mode in cell A (110).Next, a CS-only handover is performed across routing area boundaries (ofwhich PLMN boundaries are a subset) from cell A (110) to cell B (115).Then, after the CS-only handover, and without terminating the ongoing CSsession (e.g., voice call), the mobile station 105 enters DTM in cell B(115). The mobile station 105 then performs a routing area update incell B (115) (e.g., due to the change in routing area), but no locationupdate procedure is performed in cell 115 (because the CS session isstill active). At this point in the second scenario, the MSC B (150) andthe SGSN B (160) have different knowledge of the mobile station's RPLMNand EPLMN list and, like for the first example scenario above, during apotential DTM handover to CSG cell C (120), the SGSN's CSG access checkwould pass, whereas the MSC's CSG access check would fail. Accordingly,when prior CSG access checking rules are used, the DTM handover to CSGcell C (120) would fail although the CSG access check performed by theSGSN B (160) passed.

A third example scenario which may occur in the example of FIG. 2further illustrates possible consequences that may occur when prior CSGaccess checking rules are used in mobile networks. In the third examplescenario illustrated by FIG. 2, assume that, when the mobile station 105begins in cell A (110), its RPLMN is PLMN A and its EPLMN list containsPLMN C. The mobile station 105 then enters CS connected mode andcompletes a CS-only handover to cell B (115) in PLMN B Immediately afterthe handover, the mobile station's RPLMN is still PLMN A. Also, themobile station's CSG whitelist is passed to MSC B (150), but MSC B (150)does not yet know the RPLMN or the EPLMN list of the mobile station 105(e.g., because a location update cannot be performed while the CSsession is active).

Next, assume that the mobile station 105 detects CSG cell C (120) andperforms a CSG access check to determine whether: (i) the CSG cell'sPLMN and CSG ID are in the whitelist; and (ii) that the CSG cell's PLMNID corresponds to the mobile station's RPLMN or is in the mobilestation's EPLMN list. In the illustrated example, both portions of theCSG access check pass and, thus, the mobile station 105 sends ameasurement report for the CSG cell 120 to the BSS 140.

In response to receiving the measurement report, the BSS 140 initiates aCS-only handover to the CSG cell 120 for the mobile station 105. Thiscauses MSC B (150) to perform a CSG check to determine whether: (i) theCSG cell's PLMN and CSG ID are in the CSG whitelist of the mobilestation 105; and (ii) whether the CSG cell's PLMN ID corresponds to themobile station's RPLMN or is in the mobile station's EPLMN list. In theillustrated example, the first portion of the CSG access check passesbecause MSC B (150) received the mobile station's CSG whitelist from MSCA (145) due to the CS-only handover. However, in the illustrated examplescenario, MSC B (150) does not know the mobile station's EPLMN list(which contains PLMN C, which is the PLMN of the CSG cell 120) and,therefore, the second portion of the CSG access check performed by MSC B(150) fails. Thus, when prior CSG access checking rules are used, theCS-only handover to CSG cell C (120) fails due to the MSC's access checkhaving failed.

In contrast, consider an example PS-only handover scenario in which thePS-only handover to CSG cell C (120) succeeds. In this example scenario,the mobile station 105 begins in cell A (110), and its RPLMN is PLMN A,whereas its EPLMN list is empty. The mobile station 105 then enters PSconnected mode and completes a PS-only handover to cell B (115) in PLMNB. Immediately after the handover (e.g., before any routing areaupdate), the mobile station's RPLMN is still PLMN A. Also, the mobilestation's CSG whitelist is passed to SGSN B (160). Then, when the mobilestation 105 performs a routing area update (e.g., which is permittedalthough the PS session is still active), the RPLMN for the UE becomesPLMN B and assume that the EPLMN list provided in the update includesPLMN C. At this point in the scenario, SGSN B (160) knows the RPLMN andEPLMN list for the mobile station 105.

Next, assume that the mobile station 105 detects CSG cell C (120) andperforms a CSG access check to determine whether: (i) the CSG cell'sPLMN and CSG ID are in the whitelist; and (ii) that the CSG cell's PLMNID corresponds to the mobile station's RPLMN or is in the mobilestation's EPLMN list. In the illustrated example, both portions of theCSG access check pass and, thus, the mobile station 105 sends ameasurement report for the CSG cell 120 to the BSS 140.

In response to receiving the measurement report, the BSS 140 initiates aPS-only handover to the CSG cell 120 for the mobile station 105. Thiscauses SGSN B (160) to perform a CSG check to determine whether: (i) theCSG cell's PLMN and CSG ID are in the CSG whitelist of the mobilestation 105; and (ii) whether the CSG cell's PLMN ID corresponds to themobile station's RPLMN or is in the mobile station's EPLMN list. In theillustrated example, the first portion of the CSG access check passesbecause SGSN B (160) received the mobile station's CSG whitelist fromSGSN A (150) due to the PS-only handover. In this example scenario, thesecond portion of the access check performed by SGSN B (160) also passesbecause, due to the routing area update, SGSN B (160) knows the mobilestation's EPLMN list (which contains PLMN C, which is the PLMN of theCSG cell 120). Accordingly, the PS-only handover to CSG cell C (120)succeeds.

With reference to the example of FIG. 2, other problems related to CSGaccess checking can arise if, for example, the EPLMN list from cell A(110) includes PLMN C (which is assumed to be the PLMN ID for the CSGcell 120), but the EPLMN list that is obtained during a routing areaupdate in cell B (115) does not include PLMN C. In such an example,after a CS-only handover, the mobile station's CSG access check wouldpass because no location update can occur while the CS session is activeand, thus, PLMN C is still in the mobile station's unmodified EPLMNlist. However, after a DTM handover and a routing area update, themobile station's CSG access check would pass because the new EPLMN listobtained by the routing area update does not contain PLMN C.

The foregoing examples illustrate problems that can occur using priorCSG access checking rules under scenarios in which a mobile station(e.g., the mobile station 105) and the CN nodes (e.g., the MSC 155 andthe SGSN 160) have different knowledge concerning the PLMN information(e.g., the RPLMN and EPLMN list) associated with the mobile station 105.In the following, let the RPLMN and EPLMN list that the mobile station105 has prior to handover be referred to as “List A,” and let the RPLMNand EPLMN list obtained by the mobile station 105 from a subsequentrouting area update procedure be referred to as “List B.” Table 1summarizes example scenarios in which, when the mobile station 105 isdetermining whether to report the target CSG cell 120 (e.g., via ameasurement report to be sent to the BSS 120, which may cause the BSS120 to initiate a handover of the mobile station 105 to the target CSGcell 120), the PLMN information known by the MSC 155 for the mobilestation 105 is different from the PLMN information known by the SGSN 160for the mobile station 105, and/or is different from the PLMNinformation known by the mobile station 105 itself.

TABLE 1 UE UE PLMN RAU performed PLMN PLMN PLMN list Operating list atHandover immediately list at list at at UE after Mode start is DTM?after handover? new MSC new SGSN handover CS-only List A No No Unknownn/a List A PS-only List A No Yes n/a List B List B DTM List A Yes YesUnknown List B List B

FIGS. 3-6 illustrate respective block diagrams of an example MSC 300, anexample implementation of the mobile station 105, and example BSS 500and an example SGSN 600 that individually and/or collectively canimplement one or more example approaches disclosed above and in greaterdetail below for checking access to CSG cells (e.g., the CSG cell 120)in the mobile network 100. The MSC 300 of FIG. 3 can be used toimplement MSC A (145) and/or MSC B (150), the BSS 500 of FIG. 5 can beused to implement BSS A (135) and/or BSS B (140), and the SGSN 600 canbe used to implement SGSN A (155) and/or SGSN B (160). As described ingreater detail below, the CSG access checking approaches implemented bythe MSC 300, mobile station 105, BSS 500 and SGSN 600 can, among otherthings, address at least some of the problems discussed above that mayoccur with prior CSG access checking rules when the PLMN informationknown by the MSC 300 for the mobile station 105 is different from thePLMN information known by the SGSN 600 for the mobile station 105,and/or is different from the PLMN information known by the mobilestation 105 itself (see Table 1).

Turning to FIG. 3, the example MSC 300 may be used to implement MSC A(145) and/or MSC B (150). For convenience, and without loss ofgenerality, the MSC 300 is described from the perspective ofimplementing MSC B (150). In the illustrated example, the MSC 300includes an example CSG whitelist receiver 305 to receive CSGwhitelist(s) for UEs, such as the mobile station 105, served by the MSC300. For a particular UE, the CSG whitelist receiver 305 receives theUE's CSG whitelist from, for example, a prior (or source) MSC (e.g.,such as the MSC 145) that previously served the UE.

The MSC 300 of FIG. 3 also includes an example PLMN information receiver310 to receive PLMN information for UEs, such as the mobile station 105,served by the MSC 300. For example, the PLMN information received by thePLMN information receiver 310 can correspond to the RPLMN and EPLMN listdetermined for the UE during a most recent CS domain registrationprocedure, such as a location update procedure.

The MSC 300 of FIG. 3 also includes an example CSG access checkcontroller 315 to control the CSG access checks performed by the MSC 300for the UEs served by the MSC 300. In some examples, the MSC 300 of FIG.3 further includes an example handover status receiver 320 to receive astatus of a handover being performed by a UE being served by the MSC300. Operation of the CSG whitelist receiver 305, the PLMN informationreceiver 310, the CSG access check controller 315 and the handoverstatus receiver 320 of the MSC 300 to implement one or more disclosedexample approaches for checking access to CSG cells in the mobilenetwork 100 is described in greater detail below.

Turning to FIG. 4, the example implementation of the mobile station 105illustrated therein includes an example CSG access checker 405 toperform CSG access checks using one or more of an example CSG whitelist410, example PS domain PLMN information 415 and/or example CS domainPLMN information 420. As described above, the CSG whitelist 410includes, for example, data tuples containing CSG IDs and PLMN IDs forwhich the mobile station 105 has been granted access. The PS domain PLMNinformation 415 includes, for example, the RPLMN and EPLMN list obtainedby the mobile station 105 during a most recent PS domain registrationprocedure (e.g., such as a routing area update procedure). The CS domainPLMN information 420 includes, for example, the RPLMN and EPLMN listobtained by the mobile station 105 during a most recent CS domainregistration procedure (e.g., such as a location update procedure).

In some examples, the mobile station 105 of FIG. 4 also includes anexample access check identifier 425 to identify which of multiplepossible CSG access checks performed by the CSG access checker 405 hassucceeded and, thus, indicate that the mobile station 105 can access atarget CSG cell. In some examples, the mobile station 105 of FIG. 4further includes an example message transceiver 430 to send messages,which relate to the CSG access checking performed by the mobile station105, to a serving BSS (e.g., such as the BSS 500, the BSS 135, the BSS140, etc.). Operation of the CSG access checker 405, the access checkidentifier 425 and the message transceiver 430 of the mobile station 105to implement one or more disclosed example approaches for checkingaccess to CSG cells in the mobile network 100 is described in greaterdetail below.

Turning to FIG. 5, the example BSS 500 may be used to implement BSS A(135) and/or BSS B (140). For convenience, and without loss ofgenerality, the BSS 500 is described from the perspective ofimplementing BSS B (140). In some examples, the BSS 500 includes anexample handover type signaler 505 to send messages indicating the typeof handover procedures to be performed for UEs, such as the mobilestation 105, undergoing handover and served by the BSS 500. In someexamples, the BSS 500 additionally or alternatively includes an exampleaccess check selector 510 to determine which of multiple possible CSGaccess checks have been reported by a UE, such as the mobile station105, as being successful and, thus, indicate that the mobile station 105can access a target CSG cell. In some examples, the BSS 500 additionallyor alternatively includes an example PS domain access check processor515 to process CSG access check results provided by PS domain CN nodes(such as the SGSN 600, the SGSN 155 and/or the SGSN 160) for UEs, suchas the mobile station 105, attempting to access target CSG cells.Operation of the handover type signaler 505, the access check selector510 and the PS domain access check processor 515 of the BSS 500 toimplement one or more disclosed example approaches for checking accessto CSG cells in the mobile network 100 is described in greater detailbelow.

Turning to FIG. 6, the example SGSN 600 may be used to implement SGSN A(155) and/or SGSN B (160). For convenience, and without loss ofgenerality, the SGSN 600 is described from the perspective ofimplementing SGSN B (160). In some examples, the SGSN 600 includes anexample CSG access check controller 605 to control the CSG access checksperformed by the SGSN 600 for the UEs served by the SGSN 600. In someexamples, the SGSN 600 of FIG. 6 additionally or alternatively includesan example access check result reporter 610 to report results of CSGaccess checks performs by the SGSN 600 to a BSS (e.g., such as the BSS500, the BSS 135, the BSS 140, etc.). Operation of the CSG access checkcontroller 605 and the access check result reporter 610 of the SGSN 600to implement one or more disclosed example approaches for checkingaccess to CSG cells in the mobile network 100 is described in greaterdetail below.

A first example approach for checking access to CSG cells disclosedherein can be implemented by the MSC 300. In this first exampleapproach, the MSC 300 (e.g., via its PLMN information receiver 310)obtains CS domain PLMN information (e.g., the RPLMN and EPLMN list) fora UE, such as the mobile station 105, from a prior (source) MSC (such asthe MSC 145) that previously served the UE. For example, the MSC 300,via its PLMN information receiver 310, can receive CS domain PLMNinformation for a UE, which performed a handover into the MSC's coveragearea, from the source MSC and without a CS domain registration procedure(e.g., location update procedure) being required. Additionally, the MSC300, via its CSG whitelist receiver 305, can receive the CSG whitelistfor the UE, which performed a handover into the MSC's coverage area,from the source MSC. The MSC 300 can then use the received CSG whitelistand CS domain PLMN information to perform CSG access checking for the UE(e.g., if a handover of the UE to a CSG cell is subsequently attempted).In some examples, the PLMN information receiver 310 receives the CSdomain PLMN information from the source MSC via a mobile applicationpart (MAP) interface.

This first example approach for checking access to CSG cells addressesat least some of the problems described above associated with performingCSG access checks after a CS-only handover. In particular, in the firstexample approach, and with reference to Table 1 above, the MSC 300 canuse the RPLMN and EPLMN list information (e.g., List A in Table 1)obtained from the source MSC and corresponding to a most recentCS-domain (or combined CS and PS domain) registration procedure toperform CSG access checking, and this PLMN information will beconsistent with the RPLMN and EPLMN list information (e.g., List A inTable 1) at the UE. Table 2 illustrates how the first example approachfor checking access to CSG cells changes the scenario results shown inTable 1. As shown in Table 2, the first example approach for checkingaccess to CSG cells addresses the CS-only handover scenario (e.g.,because the UE and MSC both have List A), but may not address the DTMhandover scenario (e.g., if List A and List B are different).

TABLE 2 UE UE PLMN RAU performed PLMN PLMN PLMN list Operating list atHandover immediately list at list at at UE after Mode start is DTM?after handover? new MSC new SGSN handover CS-only List A No No List An/a List A PS-only List A No Yes n/a List B List B DTM List A Yes YesList A List B List B

A second example approach for checking access to CSG cells disclosedherein is an enhancement of the first example approach described aboveand supports DTM handover. Under the second example approach, in a DTMhandover to a target CSG cell, the serving SGSN refrains from performingthe CSG access check, and the UE uses a CS domain RPLMN and EPLMN listfor performing its CSG access check. This second example approach can beimplemented by the MSC 300, the mobile station 105, the BSS 500 and theSGSN 600. In the second example approach, the MSC 300 operates inaccordance with the first example approach described above for checkingaccess to CSG cells. As such, when the mobile station 105 attempts toaccess a CSG cell (e.g., the CSG cell 120) after a CS handover or DTMhandover, the MSC 300 (e.g., implementing the MSC 150) uses the RPLMNand EPLMN list information (e.g., List A in Table 1) obtained from thesource MSC (e.g., the MSC 145) and corresponding to a most recentCS-domain (or combined CS and PS domain) registration procedure toperform CSG access checking for the UE.

Additionally, in the second example approach for checking access to CSGcells, the mobile station 105 uses the CS domain PLMN info 420 toperform CSG access checking (e.g., using its CSG access checker 405), asdescribed above. The CS domain PLMN info 420 used by the CSG accesschecker 405 to perform CSG access checking at the mobile station 105corresponds to the RPLMN and EPLMN list information (e.g., List A inTable 1) obtained via a most recent CS-domain (or combined CS and PSdomain) registration procedure and, thus, is consistent with the PLMNinformation being used by the MSC 300 to perform CSG access checking. Insome examples, to ensure that the CS domain PLMN info 420 is availablewhen performing CSG access checking, the mobile station 105 stores theRPLMN and EPLMN list information obtained via a most recent CS-domainregistration procedure before obtaining a new RPLMN and EPLMN list via asubsequent PS domain registration procedure.

When a subsequent DTM handover of the mobile station 105 to a CSG cell,(e.g., the CSG cell 120) is attempted, the second example approach forchecking access to CSG cells further involves the BSS 500 (e.g.,implementing the BSS 140) signaling (e.g., via its handover typesignaler 505) the SGSN 600 (e.g., implementing the SGSN 160) to informthe SGSN 600 that the handover being performed for the mobile station105 is a DTM handover. In response to receiving the signaling, the SGSN600 (e.g., via its CSG access check controller 605), causes the SGSN 600to omit (e.g., disable) CSG access checking (or at least the PLMNchecking portion of the CSG access check) when determining whether thePS-domain portion of the DTM handover can proceed to the target CSGcell. As such, CSG access checking in the second example approach relieson the CS domain PLMN information known by the MSC 300 and the mobilestation 105 to check and confirm that the mobile station 105 ispermitted to access the target CSG cell. In some examples, the BSS 500signals the type of handover being performed to the SGSN 600 via anadditional information element (IE), such as a “DTM Indication” IE,included in the PS-HANDOVER-REQUIRED message (see 3GPP TS 48.018) sentfrom the BSS 500 to the SGSN 600 during the PS handover preparationphase (see 3GPP TS 43.029).

A third example approach for checking access to CSG cells disclosedherein can be implemented by the MSC 300, the mobile station 105 and theBSS 500. The third example approach for checking access to CSG cells isapplicable for a DTM handover of a UE (e.g., the mobile station 105) toa CSG cell (e.g., the CSG cell 120) after a DTM handover, or after aCS-only handover. In this third example approach for checking access toCSG cells, the mobile station 105 uses a PS domain RPLMN and EPLMN listto perform its CSG access check, and the serving MSC 300 does notperform a CSG access check. In an example implementation, the BSS 600(e.g., implementing the BSS 140) instructs (e.g., via its handover typesignaler 505) the MSC 300 (e.g., implementing the MSC 150) that thehandover is a DTM handover. In response, the MSC 300 (e.g., via its CSGaccess check controller 315), causes the MSC 300 to omit (e.g., disable)CSG access checking when determining whether the CS-domain portion ofthe DTM handover can proceed to the target CSG cell.

In the third example approach for checking access to CSG cells, themobile station 105 in DTM uses the PS domain PLMN info 415 to performCSG access checking (e.g., using its CSG access checker 405) todetermine whether to report a target CSG cell, as described above. ThePS domain PLMN info 420 used by the CSG access checker 405 to performCSG access checking at the mobile station 105 corresponds to the RPLMNand EPLMN list information (e.g., List B in Table 1) obtained via a mostrecent PS-domain registration procedure (e.g., a routing area updateprocedure) and, thus, is consistent with the PLMN information being usedby the SGSN (e.g., the SGSN 160) to perform CSG access checking as partof the PS-domain portion of the DTM handover to the target CSG cell.

In this third example approach for checking access to CSG cells, on thenetwork side, only the SGSN performs the complete CSG access check.However, if the PS domain portion of the handover fails, the serving BSS200 still needs to know whether the CSG access check passed or failed.Otherwise, the serving BSS 200 could assume that the failure was fornon-access check reasons, and carry on with a CS-only handover (becausea CS-only handover is a valid outcome if there is failure of the PS partof DTM handover).

Furthermore, this third example approach for checking access to CSGcells is applicable only for DTM handover to the target CSG cell (e.g.,the CSG cell 120) in which the mobile station 105 is in DTM and the BSS200 (e.g., implementing the BSS 140) attempts a DTM handover to thetarget CSG cell. Conversely, if the BSS 200 attempts a CS-only handoverto the target CSG cell while the mobile station 105 is currently in DTM,there is currently no mechanism for the mobile station 105 to knowwhether the BSS 200 is attempting a DTM handover or a CS-only handover.Thus, under the third example approach, the mobile station 105 would usethe PS-domain PLMN information (e.g., List B in Table 1), whereas theMSC 300 has either no PLMN information (because a CS domain registrationprocedure cannot be performed while the CS session in DTM is active) or,in the case of the first and second example approaches, has potentiallydifferent CS-domain PLMN information (e.g., List A in Table 1).

A fourth example approach for checking access to CSG cells disclosedherein can be implemented by the MSC 300, the mobile station 105 and theBSS 500, and involves the MSC 300 performing a modified CSG accesscheck. The fourth example approach for checking access to CSG cells,like the third example approach, is applicable for a DTM handover of theUE (e.g., the mobile station 105) to a CSG cell (e.g., the CSG cell 120)after a DTM handover, or after a CS-only handover. In the fourth exampleapproach for checking access to CSG cells, as in the third exampleapproach described above, the mobile station 105 uses the PS domain PLMNinfo 415 (e.g., the PS domain RPLMN and EPLMN list corresponding to ListB in Table 1) to perform CSG access checking (e.g., using its CSG accesschecker 405) while in DTM and determining whether to report a target CSGcell (e.g., the CSG cell 120). Furthermore, in contrast with the thirdexample approach described above, the MSC 300 (e.g., implementing theMSC 150) also performs a CSG access check, but omits the PLMN portion ofthe check (e.g., and just checks whether the CSG ID of the target CSGcell is in the mobile station's CSG whitelist). This fourth exampleapproach for checking access to CSG cells is limited to DTM handovers tothe target CSG cell for reasons similar to those for the third exampleapproach described above.

A fifth example approach for checking access to CSG cells disclosedherein can be implemented by the mobile station 105 and involves havingthe mobile station 105 use both old and new RPLMN and EPLMN lists whenperforming CSG access checking. This fifth example approach addresses atleast some of the issues associated with the first through fourthexample approaches described above. The fifth example approach forchecking access to CSG cell attempts to reduce the risk that the mobilestation's CSG access check is inconsistent with either of the CSG accesschecks performed by the service SGSN and MSC, regardless of whether theywould actually be carried out during a handover to a target CSG cell. Toreduce this risk, in the fifth example approach for checking access toCSG cells, the mobile station 105 performs two CSG access checks (e.g.,using its CSG access checker 405) to determine whether the mobilestation 105 can access the target CSG cell. For example, the mobilestation 105 performs a first CSG access check (e.g., with its CSG accesschecker 405) using the PS domain PLMN info 415 (e.g., the PS domainRPLMN and EPLMN list corresponding to List B in Table 1) and a secondCSG access check (e.g., with its CSG access checker 405) using the CSdomain PLMN info 420 (e.g., the CS domain RPLMN and EPLMN listcorresponding to List A in Table 1). The mobile station 105 thenrequires both CSG access checks (e.g., corresponding to CSG accesschecking using both the CS domain PLMN information in the serving MSCand obtained via the most recent CS-domain registration, and the PSdomain PLMN information in the serving SGSN and obtained via the mostrecent PS-domain registration) to be successful in order for the mobilestation 105 to determine that it can access the target CSG cell and,thus, whether it can send a measurement report for the CSG cell (e.g.,to initiate a handover).

By requiring both access checks performed by the mobile station 105 tobe successful in order to perform a handover to the target CSG cell, thefifth example approach for checking access to CSG cells ensures that thePLMN ID of the CSG cell is in both the {RPLMN, EPLMN} list as used inthe CS domain in the old cell (e.g., and as obtained via the most recentCS domain registration procedure) and the {RPLMN, EPLMN} list obtainedvia a later PS domain registration procedure. Accordingly, if both CSGaccess checks are performed and successful in the mobile station 105,the corresponding access checks in the MSC and SGSN will also pass.Thus, the fifth example approach for checking access to CSG cells causesthe mobile station 105 to limit its reporting of a target CSG cell(e.g., the CSG cell 120) to situations in which the CSG access testsperformed by the serving MSC (e.g., the MSC 150) and the serving SGSN(e.g., the SGSN 160) will both pass. Accordingly, this fifth exampleapproach can be implemented by the mobile station 105 without impactingthe serving MSC or SGSN.

A sixth example approach for checking access to CSG cells disclosedherein is based on synchronizing operation between the BSS and UE andcan be implemented by the mobile station 105 and the BSS 500. As notedabove, a prior 3GPP-compliant UE does not know whether the BSS willultimately initiate a DTM handover or CS-only handover when the UE isdetermining whether it can access a target CSG cell and, thus, when itis determining whether to send a measurement report including a targetCSG cell. As such, if the CSG access check behavior in the core network(or the outcome(s) thereof) for DTM handover is potentially differentfrom that for a CS-only handover, a prior 3GPP-compliant UE does notknow which CSG access check will ultimately be relied upon by thenetwork. To avoid at least some of the problems mentioned above, itwould be desirable if the UE could synchronize its CSG access check withthe access check the core network (e.g., the MSC and/or SGSN) willperform.

A first example implementation of the sixth example approach forchecking access to CSG cells achieves such synchronization by having themobile station 105, which is determining whether to report (e.g., via ameasurement report) a CSG cell (e.g., the CSG cell 120), perform eithera first CSG access check (e.g., with its CSG access checker 405) usingthe PS domain PLMN info 415 (e.g., the PS domain RPLMN and EPLMN listcorresponding to List B in Table 1) or a second CSG access check (e.g.,with its CSG access checker 405) using the CS domain PLMN info 420(e.g., the CS domain RPLMN and EPLMN list corresponding to List A inTable 1). The mobile station 105 then sends a message (e.g., preparedvia its access check identifier 425 and sent via its message transceiver430) to the BSS 500 (e.g., implementing the BSS 140) indicating whichCSG access check was performed by the mobile station 105. In response tothe message, the BSS 500 requests (e.g., via its access check selector510) the serving SGSN to perform the CSG access check (e.g., the SGSN160) if the mobile station 105 reports that the first check wasperformed, or the serving MSC to perform the CSG access check (e.g., theMSC 150) if the mobile station 105 reports that the second check wasperformed. In some examples, the BSS 500 requests (e.g., via its accesscheck selector 510) that both the serving SGSN and the serving MSCperform the CSG access check (e.g., the SGSN 160) if the mobile station105 reports that both the first check and the second check wereperformed. To avoid the need for modifying the signaling in the MS toBSS direction, the selection of the which access check to perform at themobile station 105 can be preconfigured, specified via controlinformation transmitted by the BSS 500 to the mobile station 105, etc.In such examples, the BSS 500 can request the core network access checksaccordingly (e.g., consistent with the configuration of and/or signalingsent to the mobile station 105).

A second example implementation of the sixth example approach forchecking access to CSG cells achieves such synchronization by having themobile station 105, which is determining whether to report a CSG cell(e.g., the CSG cell 120), perform both a first CSG access check (e.g.,with its CSG access checker 405) using the PS domain PLMN info 415(e.g., the PS domain RPLMN and EPLMN list corresponding to List B inTable 1) and a second CSG access check (e.g., with its CSG accesschecker 405) using the CS domain PLMN info 420 (e.g., the CS domainRPLMN and EPLMN list corresponding to List A in Table 1). The mobilestation 105 then sends a message (e.g., prepared via its access checkidentifier 425 and sent via its message transceiver 430) to the BSS 500(e.g., implementing the BSS 140) indicating which of the CSG accesscheck(s) performed by the mobile station 105 succeeded and, thus,indicated that the mobile station 105 can access the target CSG cell. Inresponse to the message, the BSS 500 requests (e.g., via its accesscheck selector 510) the serving SGSN to perform the CSG access checkresult (e.g., the SGSN 160) if the mobile station 105 reports that thefirst check succeeded, or the serving MSC to perform the CSG accesscheck result (e.g., the MSC 150) if the mobile station 105 reports thatthe second check was performed. In some examples, the BSS 500 requests(e.g., via its access check selector 510) that both the serving SGSN andthe serving MSC perform the CSG access check (e.g., the SGSN 160) if themobile station 105 reports that both of its checks succeeded.

A third example implementation of the sixth example approach forchecking access to CSG cells achieves such synchronization by having themobile station 105, which is determining whether to report a CSG cell(e.g., the CSG cell 120), perform both a first CSG access check (e.g.,with its CSG access checker 405) using the PS domain PLMN info 415(e.g., the PS domain RPLMN and EPLMN list corresponding to List B inTable 1) and a second CSG access check (e.g., with its CSG accesschecker 405) using the CS domain PLMN info 420 (e.g., the CS domainRPLMN and EPLMN list corresponding to List A in Table 1). The mobilestation 105 then sends a measurement report for the target CSG cell tothe BSS 500 (e.g., implementing the BSS 140), which indicates that themobile station 105 can access the target CSG cell (and, thus, can beused to initiate a handover), only if both CSG access checks aresuccessful (which is similar to the fifth example approach describedabove for checking access to CSG cells).

In some examples, the mobile station 105 can include an indication ofwhich CSG access check was used and/or which succeeded in themeasurement report for the target CSG cell that is sent to the BSS 500.In other examples, the mobile station 105 can send a separate message tothe BSS 500 to indicate which CSG access check was used to check theaccess to the target CSG cell, and/or which succeeded.

In some examples, the BSS 500 is configured to always attempt a DTMhandover to a CSG cell (e.g., the CSG cell 120) for a UE, such as themobile station 105, that is in DTM when it is attempting to perform ahandover to the target CSG cell. The mobile station 105 then alwaysapplies the DTM-relevant CSG access check (e.g., based on the PS domainPLMN info 415 or the PS domain RPLMN and EPLMN list corresponding toList B in Table 1). Conversely, in some examples, the BSS 500 isconfigured to always attempt a CS handover to a CSG cell (e.g., the CSGcell 120) for a UE, such as the mobile station 105, that is in DTM whenthe BSS 500 decides to handover the UE to the target CSG cell. Themobile station 105 then always applies the CS-only CSG access check(e.g., based on the CS domain PLMN info 420 or the CS domain RPLMN andEPLMN list corresponding to List A in Table 1). Such examples involve noadditional signaling between the BSS 500 and the mobile station 105.

In some examples, the BSS 500 informs a UE, such as the mobile station105, beforehand of which CSG access check option the BSS 500 will use sothe UE knows which test to apply. The UE then applies the appropriateCSG access check. This signaling could be added to one or more DTMassignment messages, which may be any message that can cause a mobile toenter DTM (see 3GPP TS 44.018 and 44.060). In some examples, anindication that, for example, the BSS 500 does not support DTM handoverwould suffice in that it indicates that all handovers will be CS-only innature.

In yet another example implementation of the sixth example approach forchecking access to CSG cells, which is related to the second exampleimplementation described above, an MS that supports handover to CSGcells, such as the mobile station 105, shall store the EPLMN list andRPLMN that were valid after the most recent of any successful locationupdating procedure, combined GPRS attach procedure, or combined routingarea updating procedure separately from the EPLMN list and RPLMNindicated in the routing area update procedure. The EPLMN list and RPLMNthat were valid after the most recent location updating procedure arereferred to as the “CS EPLMN list and RPLMN” and are not modified by arouting area update procedure.

In such an example, the mobile station 105 in dedicated mode or dualtransfer mode may report a UTRAN CSG cell or hybrid cell if: (i) themobile station 105 has received the UTRAN CSG Cells ReportingDescription IE from the network 100 in the SI2quater or MEASUREMENTINFORMATION message; (ii) the mobile station 105 has determined that itis allowed to access the cell, i.e. the CSG ID and the PLMN ID of theCSG cell or hybrid cell matches one of the CSG IDs with their associatedPLMN IDs stored in its CSG whitelist and either (a) the PLMN ID of theCSG cell or hybrid cell, for the mobile station 105 when in dedicatedmode, matches either the PLMN ID of either the RPLMN or one of theEPLMNs (if any) in the “CS EPLMN list and RPLMN” or, if the mobilestation 105 does not have a “CS EPLMN list and RPLMN”, either the RPLMNor one of the EPLMNs (if any) received during latest registration orregistration update with CS domain, or (b) the PLMN ID of the CSG cellor hybrid cell, for the mobile station 105 when in dual transfer mode,meets the requirement for the mobile station 105 when in dedicated modeor (if different) matches either the registered PLMN ID or is in thelist of equivalent PLMNs. (Note that the “CS EPLMN list and RPLMN” maybe different from the RPLMN and EPLMN list if the mobile station 105 hasperformed a routing area update since performing a CS domainregistration or registration update procedure.) Also, the mobile station105, when in DTM or when it has a “CS EPLMN list and RPLMN” which doesnot match the RPLMN and EPLMN list, reports which requirements are metin a DTM_ACCESS_CHECK_RESULT field in a MEASUREMENT REPORT message or anENHANCED MEASUREMENT REPORT message. An example of such aDTM_ACCESS_CHECK_RESULT field is illustrated in Table 3:

TABLE 3 DTM_ACCESS CHECK_RESULT (2 bit field) This field shall be set to‘00’ by an MS which has a “CS EPLMN list and RPLMN” which matches theRPLMN and EPLMN list. Otherwise, the mobile station shall set this fieldas follows: bit 2 1 0 0 MS has a “CS EPLMN list and RPLMN” which matchesthe RPLMN and EPLMN list (e.g. MS is not in DTM) 0 1 PLMN ID of CSG cellmeets the requirement for an MS in dedicated mode only; the PLMN ID ofthe CSG cell does not match either the registered PLMN ID or is in thelist of equivalent PLMNs 1 0 PLMN ID of CSG cell does not meet therequirement for an MS in dedicated mode; the PLMN ID of the CSG cellmatches either the registered PLMN ID or is in the list of equivalentPLMNs 1 1 PLMN ID of CSG cell meets the requirement for an MS indedicated mode and the PLMN ID of the CSG cell matches either theregistered PLMN ID or is in the list of equivalent PLMNs

In a further example implementation of the sixth example approach forchecking access to CSG cells, which is related to the third exampleimplementation described above, an MS that supports handover to CSGcells, such as the mobile station 105, shall store the EPLMN list andRPLMN that were valid after the most recent of any successful locationupdating procedure, combined GPRS attach procedure, or combined routingarea updating procedure separately from the EPLMN list and RPLMNindicated in the routing area update procedure. The EPLMN list and RPLMNthat were valid after the most recent location updating procedure arereferred to as the “CS EPLMN list and RPLMN” and are not modified by arouting area update procedure.

In such an example, the mobile station 105 in dedicated mode or dualtransfer mode may report a UTRAN CSG cell or hybrid cell if: (i) themobile station 105 has received the UTRAN CSG Cells ReportingDescription IE from the network in the SI2quater or MEASUREMENTINFORMATION message; (ii) the mobile station 105 has determined that itis allowed to access the cell, i.e. the CSG ID and the PLMN ID of theCSG cell or hybrid cell matches one of the CSG IDs with their associatedPLMN IDs stored in its CSG whitelist and either (a) the PLMN ID of theCSG cell or hybrid cell, for the mobile station 105 when in dedicatedmode, matches either the PLMN ID of either the RPLMN or one of theEPLMNs (if any) in the “CS EPLMN list and RPLMN” or, if the mobilestation 105 does not have a “CS EPLMN list and RPLMN”, either the RPLMNor one of the EPLMNs (if any) received during latest registration orregistration update with CS domain, or (b) the PLMN ID of the CSG cellor hybrid cell, for the mobile station 105 when in dual transfer mode,meets the requirement for the mobile station 105 in dedicated mode andmatches either the registered PLMN ID or is in the list of equivalentPLMNs. (Note that the “CS EPLMN list and RPLMN” may be different fromthe RPLMN and EPLMN list if the mobile station 105 has performed arouting area update since performing a CS domain registration orregistration update procedure.)

A seventh example approach for checking access to CSG cells disclosedherein is based on passing access check results from a serving SGSN to aserving BSS, and can be implemented by the BSS 500 and the SGSN 600. Insome examples, the MSC 300 may also be used in the implementation of theseventh example approach for checking access to CSG cells. In theseventh example approach for checking access to CSG cells, a serving MSC(e.g., the MSC 150) does not perform the CSG access check during a DTMhandover to a target CSG cell (e.g., the CSG cell 120), or its CSGaccess check results are ignored. Furthermore, the outcome of the PSdomain access check performed by the serving SGSN 600 (e.g.,implementing the SGSN 160) is made known at the BSS 500 (e.g.,implementing the BSS 140), even if the PS part of the DTM handovercannot proceed for another reason. In this way, the BSS 500 candetermine whether it is permitted to proceed with the CS-only portion ofthe DTM handover if the PS portion fails.

Prior 3GPP specifications specify at least one mechanism to indicate toa source (e.g., serving) BSS that a PS handover cannot proceed due tothe result of the CSG access check. For example, 3GPP TechnicalSpecification (TS) 48.018, subclause 8a.4, states that: “If the SGSNreceives the CSG Identifier IE in the PS-HANDOVER-REQUIRED PDU and theCell Access Mode field is set to ‘CSG cell,’ it shall perform accesscontrol as specified in 3GPP TS 29.060. If the MS is allowed to accessthe target cell, the SGSN shall continue the PS handover to the targetside as specified in 3GPP TS 29.060. If the MS is not allowed to accessthe target cell, the SGSN shall send the PS-HANDOVER-REQUIRED-NACK PDUwith the Cause IE set to ‘Invalid CSG cell’ to the source BSS. If theCell Access Mode field in the CSG Identifier IE is set to ‘Hybrid cell,’the SGSN shall provide the CSG membership status of the MS and the CSGId to the target side as specified in 3GPP TS 29.060.”

In some examples of the seventh example approach for checking access toCSG cells, the serving SGSN access check is mandatory for some or alltype of handovers to CSG cells. In a first example implementation, theserving SGSN access check may be made mandatory for all types ofhandovers to target CSG cells, an approach that does not involve newsignaling between the serving BSS 500 and the serving SGSN 600. Forexample, in one such implementation, if the SGSN receives the CSGIdentifier IE in the PS-HANDOVER-REQUIRED PDU and the Cell Access Modefield is set to “CSG cell,” it shall perform access control whether ornot the PS handover would otherwise be successful. If the MS is allowedto access the target cell, the SGSN shall continue the PS handover tothe target side as specified. If the MS is not allowed to access thetarget cell, the SGSN shall send the PS-HANDOVER-REQUIRED-NACK PDU withthe Cause IE set to “Invalid CSG cell” to the source BSS. If the CellAccess Mode field in the CSG Identifier IE is set to “Hybrid cell”, theSGSN shall provide the CSG membership status of the MS and the CSG Id tothe target side.

In a second example implementation of the seventh example approach forchecking access to CSG cells, the serving SGSN access check may be mademandatory for just DTM handovers to target CSG cells, which may requiresignaling between the BSS 500 and SGSN 600 to indicate whether a DTMhandover is being performed, but may simplify SGSN behavior for non-DTMhandover cases. For example, in one such implementation, if the SGSNreceives the CSG Identifier IE in the PS-HANDOVER-REQUIRED PDU and theCell Access Mode field is set to “CSG cell”, it shall perform accesscontrol. If the PS-HANDOVER-REQUIRED PDU included a DTM Handover IE,this access control shall be carried out whether or not the PS Handoverwould otherwise be successful. If the MS is allowed to access the targetcell, the SGSN shall continue the PS handover to the target side. If theMS is not allowed to access the target cell, the SGSN shall send thePS-HANDOVER-REQUIRED-NACK PDU with the Cause IE set to “Invalid CSGcell” to the source BSS. If the Cell Access Mode field in the CSGIdentifier IE is set to “Hybrid cell”, the SGSN shall provide the CSGmembership status of the MS and the CSG ID to the target side.

In either of the preceding example implementations, there are severalalternative ways for the serving SGSN 600 to provide (e.g., via itsaccess check result reporter 610) an SGSN indication of its access checkresult to the serving BSS 500. In a first example alternative, the“Invalid CSG cell” cause takes precedence in thePS-HANDOVER-REQUIRED-NACK PDU described above. In such an example,receipt of any other cause by the BSS 500 implies (e.g., to the BSS's PSdomain access check processor 515) the SGSN's CSG access check issuccessful. For example, in one such implementation, when the SGSN 600terminates the PS Handover Required procedure by sending aPS-HANDOVER-REQUIRED-NACK PDU to the source BSS, 500 the Cause IE is setto an appropriate value (e.g. “PFC create failure”, “Cell trafficcongestion”, “Equipment failure”, “O&M intervention”, “PS HandoverTarget not allowed”, “PS Handover not Supported in Target BSS or TargetSystem” or “Invalid CSG cell”). In such an example, “Invalid CSG cell”is indicated, if applicable, regardless of any other valid cause value.

In a second example alternative, the “Invalid CSG” cause can be sent tothe BSS 500 with another cause value. In such examples, absence of“Invalid CSG” cause implies (e.g., to the BSS's PS domain access checkprocessor 515) that the SGSN's CSG access check is successful. Forexample, in one such implementation, when the SGSN 600 terminates the PSHandover Required procedure by sending a PS-HANDOVER-REQUIRED-NACK PDUto the source BSS 500, the Cause IE should be set to an appropriatevalue (e.g. “PFC create failure”, “Cell traffic congestion”, “Equipmentfailure”, “O&M intervention”, “PS Handover Target not allowed”, “PSHandover not Supported in Target BSS or Target System” or “Invalid CSGcell”). In such an example. if “Invalid CSG cell” and one or more othercause values are applicable, the Cause IE shall indicate “Invalid CSGcell” and the Secondary Cause IE containing an additional cause may beincluded.

In a third example alternative, a separate IE is used to indicate theoutcome of the SGSN's CSG access check. Such an IE provides confirmation(e.g., to the BSS's PS domain access check processor 515) that a CSGcheck in the CN was carried out. For example, in one suchimplementation, in the case of unsuccessful PS Handover, the source BSS500 shall be notified through the PS-HANDOVER-REQUIRED-NACK PDU. If theSGSN 600 performed access control, the result of the access controlshall be indicated in the Access Check Result IE.

Any of the example alternatives for making the SGSN access checkmandatory for some or all type of handovers can be combined with any ofthe example alternatives for the serving SGSN 600 to provide an SGSNindication of its access check result to the serving BSS 500

In some examples of the seventh example approach for checking access toCSG cells, the BSS 500 (e.g., implementing the BSS 140) must wait forconfirmation from the SGSN 600 (e.g., implementing the SGSN 160) thatthe SGSN's CSG access control procedure was successful before proceedingwith a handover of the UE (e.g., the mobile station 105) to a target CSGcell (e.g., the CSG cell 120). In such examples, the BSS 500 (e.g., ascontrolled by its PS domain access check processor 515) is not permittedto proceed with either a CS-only or DTM handover to the target CSG cellbased only on the response received from the serving MSC (e.g., the MSC150). For example, in one such implementation, if, in the case of DTMhandover command to a CSG cell, the BSS 500 receives from the MSC 300 aBSSMAP HANDOVER COMMAND message and the DTM Handover Command Indicationfield element is included within the New BSS to Old BSS Information IE,the BSS 300 shall wait until it receives a PS-HANDOVER-REQUIRED-ACK PDU(if it has not already received it from the SGSN 600) which indicatesthat the access control was carried out and that the mobile station 105is allowed to access the CSG cell, then stop timer T23 and transmit the(RLC/MAC) DTM HANDOVER COMMAND radio interface message to the mobilestation 105.

In some examples of the seventh example approach for checking access toCSG cells, regardless of whether the BSS 500 (e.g., implementing the BSS140) receives a positive response from the serving MSC (e.g., the MSC150) indicating that either a CS-only or DTM handover can proceed, ifthe BSS 500 receives an indication from the SGSN 600 (e.g., implementingthe SGSN 160) that its access control procedure failed (or accesscontrol was not carried out), the BSS 500 (e.g., as controlled by its PSdomain access check processor 515) cannot proceed with the handover tothe target CSG cell (e.g., the CSG cell 120), and a new cause value canbe sent to the serving MSC 300 (e.g., for receipt by its handover statusreceiver 320) to indicate this new reason for failure. For example, inone such implementation, if the BSS 500 receives aPS-HANDOVER-REQUIRED-NACK PDU indicating that either i) the accesscontrol was not carried out, or ii) the mobile station 105 is notallowed to access the CSG cell, then the BSS 500 sends a HANDOVERFAILURE message to the MSC 300 with cause “DTM Handover—Access controlfailure” (or some other similar cause value). In some such examples, nomessage shall be sent to the mobile station 105, regardless of theresponse received from the MSC.

In some examples, one or more of the approaches for checking access toCSG cells disclosed above could be limited to scenarios in which therehas already been an inter-RAU handover (and/or inter PLMN handover)prior to attempting a handover to a target CSG cell on the basis that,prior to handover, both the serving SGSN and the serving MSC shouldperform their respective CSG access checks and, thus, obtain the sameCSG access check results.

While example manners of implementing the mobile network 100 of FIGS. 1and 2 has been illustrated in FIGS. 3-6, one or more of the elements,processes and/or devices illustrated in FIGS. 2-6 may be combined,divided, re-arranged, omitted, eliminated and/or implemented in anyother way. Further, the example mobile device 105, the example BSSs 135,140 and/or 500, the example MSCs 145, 150 and/or 300, the example SGSNs.155, 160 and/or 600, the example CSG whitelist receiver 305, the examplePLMN information receiver 310, the example CSG access check controller315, the example handover status receiver 320, the example CSG accesschecker 405, the example access check identifier 425, the examplemessage transceiver 430, the example handover type signaler 505, theexample access check selector 510, the example PS domain access checkprocessor 515, the example CSG access check controller 605, the exampleaccess check result reporter 610 and/or, more generally, the examplemobile network 100 of FIGS. 1-6 may be implemented by hardware,software, firmware and/or any combination of hardware, software and/orfirmware. Thus, for example, any of the example mobile device 105, theexample BSSs 135, 140 and/or 500, the example MSCs 145, 150 and/or 300,the example SGSNs. 155, 160 and/or 600, the example CSG whitelistreceiver 305, the example PLMN information receiver 310, the example CSGaccess check controller 315, the example handover status receiver 320,the example CSG access checker 405, the example access check identifier425, the example message transceiver 430, the example handover typesignaler 505, the example access check selector 510, the example PSdomain access check processor 515, the example CSG access checkcontroller 605, the example access check result reporter 610 and/or,more generally, the example mobile network 100 could be implemented byone or more circuit(s), programmable processor(s), application specificintegrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s))and/or field programmable logic device(s) (FPLD(s)), etc. In at leastsome example implementations, at least one of the example mobile network100, the example mobile device 105, the example BSSs 135, 140 and/or500, the example MSCs 145, 150 and/or 300, the example SGSNs. 155, 160and/or 600, the example CSG whitelist receiver 305, the example PLMNinformation receiver 310, the example CSG access check controller 315,the example handover status receiver 320, the example CSG access checker405, the example access check identifier 425, the example messagetransceiver 430, the example handover type signaler 505, the exampleaccess check selector 510, the example PS domain access check processor515, the example CSG access check controller 605, and/or the exampleaccess check result reporter 610 are hereby expressly defined to includea tangible computer readable medium such as a memory, digital versatiledisk (DVD), compact disk (CD), Blu-ray disc™, etc., storing suchsoftware and/or firmware. Further still, the example mobile network 100may include one or more elements, processes and/or devices in additionto, or instead of, those illustrated in FIGS. 1-6, and/or may includemore than one of any or all of the illustrated elements, processes anddevices.

Flowcharts representative of example processes for implementing theexample mobile network 100, the example mobile device 105, the exampleBSSs 135, 140 and/or 500, the example MSCs 145, 150 and/or 300, theexample SGSNs. 155, 160 and/or 600, the example CSG whitelist receiver305, the example PLMN information receiver 310, the example CSG accesscheck controller 315, the example handover status receiver 320, theexample CSG access checker 405, the example access check identifier 425,the example message transceiver 430, the example handover type signaler505, the example access check selector 510, the example PS domain accesscheck processor 515, the example CSG access check controller 605, and/orthe example access check result reporter 610 are shown in FIGS. 7-18. Inthese examples, the process represented by each flowchart may beimplemented by one or more programs comprising machine readableinstructions for execution by a processor, such as the processor 1912shown in the example processing system 1900 discussed below inconnection with FIG. 19. The one or more programs, or portion(s)thereof, may be embodied in software stored on a tangible computerreadable medium such as a CD-ROM, a floppy disk, a hard drive, a digitalversatile disk (DVD), a Blu-ray disc™, or a memory associated with theprocessor 1912, but the entire program or programs and/or portionsthereof could alternatively be executed by a device other than theprocessor 1912 (e.g., such as a controller and/or any other suitabledevice) and/or embodied in firmware or dedicated hardware (e.g.,implemented by an ASIC, a PLD, an FPLD, discrete logic, etc.). Also, oneor more of the processes represented by the flowchart of FIGS. 7-18, orone or more portion(s) thereof, may be implemented manually. Further,although the example processes are described with reference to theflowcharts illustrated in FIGS. 7-18, many other methods of implementingthe example mobile network 100, the example mobile device 105, theexample BSSs 135, 140 and/or 500, the example MSCs 145, 150 and/or 300,the example SGSNs. 155, 160 and/or 600, the example CSG whitelistreceiver 305, the example PLMN information receiver 310, the example CSGaccess check controller 315, the example handover status receiver 320,the example CSG access checker 405, the example access check identifier425, the example message transceiver 430, the example handover typesignaler 505, the example access check selector 510, the example PSdomain access check processor 515, the example CSG access checkcontroller 605, and/or the example access check result reporter 610 mayalternatively be used. For example, with reference to the flowchartsillustrated in FIGS. 7-18, the order of execution of the blocks may bechanged, and/or some of the blocks described may be changed, eliminated,combined and/or subdivided into multiple blocks.

As mentioned above, the example processes of FIGS. 7-18 may beimplemented using coded instructions (e.g., computer readableinstructions) stored on a tangible computer readable medium such as ahard disk drive, a flash memory, a read-only memory (ROM), a CD, a DVD,a cache, a random-access memory (RAM) and/or any other storage media inwhich information is stored for any duration (e.g., for extended timeperiods, permanently, brief instances, for temporarily buffering, and/orfor caching of the information). As used herein, the term tangiblecomputer readable medium is expressly defined to include any type ofcomputer readable storage and to exclude propagating signals.Additionally or alternatively, the example processes of FIGS. 7-18 maybe implemented using coded instructions (e.g., computer readableinstructions) stored on a non-transitory computer readable medium, suchas a flash memory, a ROM, a CD, a DVD, a cache, a random-access memory(RAM) and/or any other storage media in which information is stored forany duration (e.g., for extended time periods, permanently, briefinstances, for temporarily buffering, and/or for caching of theinformation). As used herein, the term non-transitory computer readablemedium is expressly defined to include any type of computer readablemedium and to exclude propagating signals. Also, as used herein, theterms “computer readable” and “machine readable” are consideredequivalent unless indicated otherwise. Furthermore, as used herein, whenthe phrase “at least” is used as the transition term in a preamble of aclaim, it is open-ended in the same manner as the term “comprising” isopen ended. Thus, a claim using “at least” as the transition term in itspreamble may include elements in addition to those expressly recited inthe claim.

For convenience, and without loss of generality, the example processesillustrated in FIGS. 7-18 are described from the perspective of the MSC300 implementing the MSC B (150), the BSS 500 implementing BSS B (140),the SGSN 600 implementing SGSN B (160) and the mobile station 105 beingimplemented in accordance with the example of FIG. 4. Furthermore, thefollowing descriptions of the example processes illustrated in FIGS.7-18 assume that a DTM or CS-only handover of the mobile station 105 toCSG cell C (120) is being attempted after a DTM or CS-only handover fromcell A (110) to cell B (115) has been performed, and without havingterminated the CS session (e.g., corresponding to the example scenariosillustrated in FIG. 2).

An example process 700 that may be executed to implement the example MSC300 of FIG. 3 is illustrated in FIG. 7. The example process 700 can beused by the MSC 300 to implement the first example approach for checkingaccess to CSG cells described above. With reference to the precedingfigures and associated descriptions, the process 700 of FIG. 7 beginsexecution at block 710 at which the PLMN information receiver 310 of theMSC 300 receives CS domain PLMN information (e.g., the RPLMN and EPLMNlist) for the mobile station 105 from the source MSC 145, as describedabove. At block 715, the MSC 300 then performs a CSG access check, asdescribed above, for the mobile station 105 that includes comparing thePLMN ID of CSG cell C (120) to the CS domain PLMN information obtainedat block 710.

An example process 800 that may be executed to implement the examplemobile station 105 of FIGS. 1, 2 and/or 4 is illustrated in FIG. 8. Theexample process 800 can be used by the mobile station 105 to implementthe second example approach for checking access to CSG cells describedabove. With reference to the preceding figures and associateddescriptions, the process 800 of FIG. 8 begins execution at block 805 atwhich the mobile station 105 is determining whether to report the targetCSG cell 120 (e.g., via a measurement report, which may cause thenetwork to initiated a handover to the target cell 120). At block 810,the mobile station 105 uses its CS domain PLMN info 420 to perform CSGaccess checking using its CSG access checker 405, as described above. Asdescribed above, the CS domain PLMN info 420 corresponds to the RPLMNand EPLMN list information (e.g., List A in Table 1) obtained via a mostrecent CS-domain (or combined CS and PS domain) registration procedureand, thus, is consistent with the PLMN information being used by the MSC300 to perform CSG access checking.

Respective example processes 900 and 905 that may be executed toimplement the example BSS 500 of FIG. 5 and the example SGSN 600 of FIG.6 are illustrated in FIG. 9. The example processes 900 and 905 can beused by the BSS 500 and the SGSN 600 to implement the second exampleapproach for checking access to CSG cells described above. Withreference to the preceding figures and associated descriptions, theprocess 900 of FIG. 9 begins execution at block 905 at which the BSS 500receives a measurement report for the CSG cell 120 from the mobilestation 105, which causes the BSS 500 to initiate a handover in theillustrated example. At block 915, the BSS 500 determines whether thehandover is a DTM handover. If the handover is a DTM handover (block915), then the handover type signaler 505 of the BSS 500 sends a messageto the SGSN 600 to inform the SGSN 600 that handover being attempted bythe mobile station 105 to the CSG cell 120 is a DTM handover.

Turning to the process 905 of FIG. 9, at block 925, the CSG access checkcontroller 605 of the SGSN 600 receives the message from the BSS 500indicating that the handover being attempted for the mobile station 105to the CSG cell 120 is a DTM handover. Accordingly, at block 930 the CSGaccess check controller 605 causes the SGSN 600 to omit (e.g., disable)CSG access checking (or at least the PLMN checking portion of the CSGaccess check) when determining whether the PS-domain portion of the DTMhandover can proceed to the target CSG cell.

An example process 1000 that may be executed to implement the examplemobile station 105 of FIGS. 1, 2 and/or 4 is illustrated in FIG. 10. Theexample process 1000 can be used by the mobile station 105 to implementthe third and/or fourth example approaches for checking access to CSGcells described above. With reference to the preceding figures andassociated descriptions, the process 1000 of FIG. 10 begins execution atblock 1005 at which the mobile station 105 is determining whether toreport the target CSG cell 120 (e.g., via a measurement report, whichmay cause the network to initiated a handover to the target cell 120).At block 1010, the mobile station 105 uses its PS domain PLMN info 415to perform CSG access checking using its CSG access checker 405, asdescribed above. As described above, the PS domain PLMN info 415corresponds to the RPLMN and EPLMN list information (e.g., List B inTable 1) obtained via a most recent PS-domain registration procedure(e.g., a routing area update procedure) and, thus, is consistent withthe PLMN information being used by the SGSN 600 to perform CSG accesschecking as part of the PS-domain portion of the DTM handover to thetarget CSG cell 120.

Respective example processes 1100 and 1105 that may be executed toimplement the example BSS 500 of FIG. 5 and the example MSC 300 of FIG.3 are illustrated in FIG. 11. The example processes 1100 and 1105 can beused by the BSS 500 and the MSC 300 to implement the third exampleapproach for checking access to CSG cells described above. Withreference to the preceding figures and associated descriptions, theprocess 1100 of FIG. 11 begins execution at block 1105 at which the BSS500 receives a measurement report for the CSG cell 120 from the mobilestation 105, which causes the BSS 500 to initiate a handover in theillustrated example. At block 1115, the BSS 500 determines whether thehandover is a DTM handover. If the handover is a DTM handover (block1115), then the handover type signaler 505 of the BSS 500 sends amessage to the MSC 300 to inform the MSC 300 that handover beingattempted by the mobile station 105 to the CSG cell 120 is a DTMhandover.

Turning to the process 1105 of FIG. 11, at block 1125, the CSG accesscheck controller 315 of the MSC 300 receives the message from the BSS500 indicating that the handover being attempted by the mobile station105 to the CSG cell 120 is a DTM handover. Accordingly, at block 1130the CSG access check controller 605 causes the MSC 300 to omit (e.g.,disable) CSG access checking when determining whether the CS-domainportion of the DTM handover can proceed to the target CSG cell.

Respective example processes 1200 and 1205 that may be executed toimplement the example BSS 500 of FIG. 5 and the example MSC 300 of FIG.3 are illustrated in FIG. 12. The example processes 1200 and 1205 can beused by the BSS 500 and the MSC 300 to implement the fourth exampleapproach for checking access to CSG cells described above. Withreference to the preceding figures and associated descriptions, theprocess 1200 of FIG. 12 begins execution at block 1205 at which the BSS500 receives a measurement report for the CSG cell 120 from the mobilestation 105, which causes the BSS 500 to initiate a handover in theillustrated example. At block 1215, the BSS 500 determines whether thehandover is a DTM handover. If the handover is a DTM handover (block1215), then the handover type signaler 505 of the BSS 500 sends amessage to the MSC 300 to inform the MSC 300 that handover beingattempted by the mobile station 105 to the CSG cell 120 is a DTMhandover.

Turning to the process 1205 of FIG. 12, at block 1225, the CSG accesscheck controller 315 of the MSC 300 receives the message from the BSS500 indicating that the handover being attempted by the mobile station105 to the CSG cell 120 is a DTM handover. Accordingly, at block 1230the CSG access check controller 605 causes the MSC 300 to perform CSGaccess checking for the mobile station 105 by comparing the CSG ID ofthe CSG cell 120 to the mobile station's CSG whitelist, but causes theMSC 300 to omit (e.g., disable) the portion of the CSG access checkinvolving comparing the PLMN ID of the CSG cell 120 with the PLMNinformation (e.g., the RPLMN and EPLMN list) associated with the mobilestation 105.

An example process 1300 that may be executed to implement the examplemobile station 105 of FIGS. 1, 2 and/or 4 is illustrated in FIG. 13. Theexample process 1300 can be used by the mobile station 105 to implementthe fifth example approach and/or the third example implementation ofthe sixth example approach for checking access to CSG cells describedabove. With reference to the preceding figures and associateddescriptions, the process 1300 of FIG. 13 begins execution at block 1305at which the mobile station 105 is determining whether to report thetarget CSG cell 120 (e.g., via a measurement report, which may cause thenetwork to initiated a handover to the target cell 120). At block 1310,the mobile station 105 uses its PS domain PLMN info 415 to perform afirst CSG access check with its CSG access checker 405, as describedabove. As described above, the PS domain PLMN info 415 corresponds tothe RPLMN and EPLMN list information (e.g., List B in Table 1) obtainedvia a most recent PS-domain registration procedure (e.g., a routing areaupdate procedure) and, thus, is consistent with the PLMN informationbeing used by the SGSN 600 to perform CSG access checking as part of thePS-domain portion of the DTM handover to the target CSG cell 120. Atblock 1315, the mobile station 105 uses its CS domain PLMN info 420 toperform a second CSG access check with its CSG access checker 405, asdescribed above. As described above, the CS domain PLMN info 420corresponds to the RPLMN and EPLMN list information (e.g., List A inTable 1) obtained via a most recent CS-domain registration procedure(e.g., a location update procedure) and, thus, is consistent with thePLMN information being used by the MSC 300 to perform CSG accesschecking as part of the CS-domain portion of the DTM handover to thetarget CSG cell 120.

At block 1320, the access check identifier 425 of the mobile station 105determines whether both of the CSG access checks performed at blocks1310 and 1315 succeeded and, thus, indicate that the mobile station canaccess the target CSG cell 120. If both CSG access checks succeeded(block 1320), then at block 1325 the mobile station 105 sends a message(e.g., a measurement report for the target CSG cell 120) via its messagetransceiver 430 to the BSS 500, which indicates that access to thetarget CSG cell 120 is allowed and, thus, may cause handover to the CSGcell 120 to be initiated. Conversely, if one or both of the CSG accesschecks failed (block 1320), at block 1330 the mobile stations 105 doesnot send the message (e.g., the measurement report for the target CSGcell 120) to the BSS 500 and, thus, handover is not initiated.

An example process 1400 that may be executed to implement the examplemobile station 105 of FIGS. 1, 2 and/or 4 is illustrated in FIG. 14. Theexample process 1400 can be used by the mobile station 105 to implementthe second example implementation of the sixth example approach forchecking access to CSG cells described above. With reference to thepreceding figures and associated descriptions, the process 1400 of FIG.14 begins execution at block 1405 at which the mobile station 105 isdetermining whether to report the target CSG cell 120. At block 1410,the mobile station 105 uses its PS domain PLMN info 415 to perform afirst CSG access check with its CSG access checker 405, as describedabove. As described above, the PS domain PLMN info 415 corresponds tothe RPLMN and EPLMN list information (e.g., List B in Table 1) obtainedvia a most recent PS-domain registration procedure (e.g., a routing areaupdate procedure) and, thus, is consistent with the PLMN informationbeing used by the SGSN 600 to perform CSG access checking as part of thePS-domain portion of the DTM handover to the target CSG cell 120. Atblock 1415, the mobile station 105 uses its CS domain PLMN info 420 toperform a second CSG access check with its CSG access checker 405, asdescribed above. As described above, the CS domain PLMN info 420corresponds to the RPLMN and EPLMN list information (e.g., List A inTable 1) obtained via a most recent CS-domain registration procedure(e.g., a location update procedure) and, thus, is consistent with thePLMN information being used by the MSC 300 to perform CSG accesschecking as part of the CS-domain portion of the DTM handover to thetarget CSG cell 120.

At block 1420, the access check identifier 425 of the mobile station 105determines whether at least one of the CSG access checks performed atblocks 1310 and 1315 succeeded and, thus, indicates that the mobilestation can access the target CSG cell 120. If at least one of the CSGaccess checks succeeded (block 1420), then at block 1425 the mobilestation 105 prepares a message (e.g., a measurement report for thetarget CSG cell 120) to be sent to the BSS 500, which indicates thataccess to the target CSG cell 120 is allowed and, thus, may causehandover to the CSG cell 120 to be initiated. The message prepared atblock 1425 also includes an indication of which of the CSG access checksat blocks 1310 and 1315 succeeded or, in other words, whether the firstCSG access check based on the PS domain PLMN info 415, the second CSGaccess check based on the CS domain PLMN info 420, or both, succeeded.At block 1430, the mobile station 105 sends, via its message transceiver430, the message (e.g., the measurement report for the target CSG cell120) prepared at block 1425 to the BSS 500, which indicates which CSGaccess check determined that access to the target CSG cell 120 isallowed. Conversely, if both of the CSG access checks failed (block1420), at block 1435 the mobile stations 105 does not send the message(e.g., the measurement report for the target CSG cell 120) to the BSS500 and, thus, handover is not initiated.

The mobile station 105 can support the first example implementation ofthe sixth example approach for checking access to CSG cells describedabove via a modification of the example process 1400. In particular,instead of performing the two CSG access checks at block 1410 and 1415,the mobile station 105 selects to perform either the first CSG accesscheck based on the PS domain PLMN info 415 or the second CSG accesscheck based on the CS domain PLMN info 420. If the selected check passes(e.g., see block 1420), then at block 1425 the mobile station 105includes in the message an indication of which CSG access check wasselected and successful. Operation of the example process 1400 otherwiseproceeds as described above.

An example process 1500 that may be executed to implement the exampleBSS 500 of FIG. 5 is illustrated in FIG. 15. The example process 1500can be used by the BSS 500 to implement the sixth example approach forchecking access to CSG cells described above. With reference to thepreceding figures and associated descriptions, the process 1500 of FIG.15 begins execution at block 1505 at which the access check selector 510of the BSS 500 receives a message (e.g., a measurement report) from themobile station 105 containing an indicator identifying which of a firstCSG access check based on the PS domain PLMN info 415 or a second CSGaccess check based on the CS domain PLMN info 420 (or both) wassuccessful and, thus, indicate that the mobile station 105 can accessthe target CSG cell 120. At block 1510, the access check selector 510 ofthe BSS 500 then requests that the serving SGSN 160 perform the CSGaccess check (e.g., if the mobile station 105 reports that the first CSGaccess check was performed) or requests that the serving MSC 150 performthe CSG access check (e.g., if the mobile station 105 reports that thesecond check was performed), or both, in accordance with the indicatorreceived at block 1505. The BSS 500 then uses the requested CN-side CSGaccess check result(s) when determining whether to initiate the handoverto the target CSG cell 120.

An example process 1600 that may be executed to implement the exampleSGSN 600 of FIG. 6 is illustrated in FIG. 16. The example process 1600can be used by the SGSN 600 to implement the seventh example approachfor checking access to CSG cells described above. With reference to thepreceding figures and associated descriptions, the process 1600 of FIG.16 begins execution at block 1605 at which the SGSN 600 determines thatthe mobile station 105 is attempting a DTM handover to the target CSGcell 120. For example, at block 1605 the SGSN 600 may receive a message,such as a PS-HANDOVER-REQUIRED PDU, from the BSS 500 containing a new IEindicating that the handover is a DTM handover. At block 1610, the SGSN600 performs a CSG access check, as described above, to determinewhether the mobile station 105 is able to access the target CSG cell120. As described above, the SGSN 600 performs the CSG access check atblock 1610 regardless of whether the PS handover portion of the DTMhandover would otherwise be successful or unsuccessful. At block 1615,the access check result reporter 610 of the SGSN 600 reports the resultsof its CSG access check to the BSS 500, as described above.

An example process 1700 that may be executed to implement the exampleBSS 500 of FIG. 5 is illustrated in FIG. 17. The example process 1700can be used by the BSS 500 to implement the seventh example approach forchecking access to CSG cells described above. With reference to thepreceding figures and associated descriptions, the process 1700 of FIG.17 begins execution at block 1705 at which the BSS 500 determines that aDTM handover to the target CSG cell 120 is being attempted a for themobile station 105. At block 1710, the BSS 500 waits for a message fromthe SGSN 600 providing a CSG access check result indicating whether themobile station 105 is able to access the target CSG cell 120. At block1715, the BSS 500 receives the message containing the CSG access checkresult from the SGSN 600. At block 1720, the PS domain access checkprocessor 515 of the BSS 500 processes the received message to determinethe PS domain CSG access check result returned from the SGSN 600. Forexample, at block 1720, the PS domain access check processor 515 candecode the received message in accordance with which of the examplealternatives described above was used to indicate the CSG access resultin the message.

At block 1725, the BSS 500 determines whether the received PS domainaccess check result indicates that the mobile station 105 is allowed toaccess the target CSG cell 120. If the mobile station 105 is allowed toaccess the CSG cell 120 (block 1725), then at block 1730 the BSS 500permits the DTM handover to the target CSG cell 120 to proceed (e.g.,regardless of any CS domain CSG access check result received from theMSC 300). Conversely, if the mobile station 105 is not allowed to accessthe CSG cell 120 (block 1725), then at block 1735 the BSS 500 does notpermit either a DTM handover or a CS-only handover to the target CSGcell 120 to occur (e.g., regardless of any CS domain CSG access checkresult received from the MSC 300). Furthermore, at block 1735, the BSSreports the handover failure to the MSC 300.

An example process 1800 that may be executed to implement the exampleMSC 300 of FIG. 3 is illustrated in FIG. 18. The example process 1800can be used by the MSC 300 to implement the seventh example approach forchecking access to CSG cells described above. With reference to thepreceding figures and associated descriptions, the process 1800 of FIG.18 begins execution at block 1805 at which the handover status receiver320 of the MSC 300 receives a message from the BSS 500 indicating thestatus of a DTM handover being attempted by the mobile station 105 tothe target CSG cell 120. At block 1810, the MSC 300 performs the CSdomain portion of the DTM handover in accordance with the messagereceived at block 1805. For example, if the message from the BSS 500indicates that the DTM handover has failed (e.g., because the PS domainCSG access check result from the SGSN 500 indicates a failure), then theMSC 300 will not proceed with the CS domain portion of the DTM handover.

FIG. 19 is a block diagram of an example processing system 1900 capableof executing the processes of FIGS. 7-18 to implement the example mobilenetwork 100, the example mobile device 105, the example BSSs 135, 140and/or 500, the example MSCs 145, 150 and/or 300, the example SGSNs.155, 160 and/or 600, the example CSG whitelist receiver 305, the examplePLMN information receiver 310, the example CSG access check controller315, the example handover status receiver 320, the example CSG accesschecker 405, the example access check identifier 425, the examplemessage transceiver 430, the example handover type signaler 505, theexample access check selector 510, the example PS domain access checkprocessor 515, the example CSG access check controller 605, and/or theexample access check result reporter 610 of FIGS. 1-6. The processingsystem 1900 can be, for example, a server, a personal computer, a mobilephone (e.g., a smartphone, a cell phone, etc.), a personal digitalassistant (PDA), an Internet appliance, a DVD player, a CD player, adigital video recorder, a Blu-ray player, a gaming console, a personalvideo recorder, a set top box, a digital camera, or any other type ofcomputing device.

The system 1900 of the instant example includes a processor 1912. Forexample, the processor 1912 can be implemented by one or moremicroprocessors and/or controllers from any desired family ormanufacturer.

The processor 1912 includes a local memory 1913 (e.g., a cache) and isin communication with a main memory including a volatile memory 1914 anda non-volatile memory 1916 via a bus 1918. The volatile memory 1914 maybe implemented by Static Random Access Memory (SRAM), SynchronousDynamic Random Access Memory (SDRAM), Dynamic Random Access Memory(DRAM), RAMBUS Dynamic Random Access Memory (RDRAM) and/or any othertype of random access memory device. The non-volatile memory 1916 may beimplemented by flash memory and/or any other desired type of memorydevice. Access to the main memory 1914, 1916 is controlled by a memorycontroller.

The processing system 1900 also includes an interface circuit 1920. Theinterface circuit 1920 may be implemented by any type of interfacestandard, such as an Ethernet interface, a universal serial bus (USB),and/or a PCI express interface.

One or more input devices 1922 are connected to the interface circuit1920. The input device(s) 1922 permit a user to enter data and commandsinto the processor 1912. The input device(s) can be implemented by, forexample, a keyboard, a mouse, a touchscreen, a track-pad, a trackball, atrackbar (such as an isopoint), a voice recognition system and/or anyother human-machine interface.

One or more output devices 1924 are also connected to the interfacecircuit 1920. The output devices 1924 can be implemented, for example,by display devices (e.g., a liquid crystal display, a cathode ray tubedisplay (CRT)), a printer and/or speakers. The interface circuit 1920,thus, typically includes a graphics driver card.

The interface circuit 1920 also includes a communication device, such asa modem or network interface card, to facilitate exchange of data withexternal computers via a network 1926 (e.g., an Ethernet connection, adigital subscriber line (DSL), a telephone line, coaxial cable, acellular telephone system, etc.).

The processing system 1900 also includes one or more mass storagedevices 1928 for storing machine readable instructions and data.Examples of such mass storage devices 1928 include floppy disk drives,hard drive disks, compact disk drives and digital versatile disk (DVD)drives.

Coded instructions 1932 corresponding to the instructions of FIGS. 7-18may be stored in the mass storage device 1928, in the volatile memory1914, in the non-volatile memory 1916, in the local memory 1913 and/oron a removable storage medium, such as a CD or DVD 1936.

As an alternative to implementing the methods and/or apparatus describedherein in a system such as the processing system of FIG. 19, the methodsand or apparatus described herein may be embedded in a structure such asa processor and/or an ASIC (application specific integrated circuit).

Finally, although certain example methods, apparatus and articles ofmanufacture have been described herein, the scope of coverage of thispatent is not limited thereto. On the contrary, this patent covers allmethods, apparatus and articles of manufacture fairly falling within thescope of the appended claims either literally or under the doctrine ofequivalents.

What is claimed is:
 1. A method for a mobile station, the methodcomprising: storing a second equivalent public land mobile network(EPLMN) list and a second RPLMN identifier before obtaining a firstEPLMN list and a first registered public land mobile network (RPLMN)identifier via a subsequent packet switched domain registrationprocedure; performing a first access check based on the first EPLMN listand the first RPLMN identifier to determine whether the mobile stationis allowed to access a closed subscriber group (CSG) cell; performing asecond access check based on a second EPLMN list and a second RPLMNidentifier to determine whether the mobile station is allowed to accessthe CSG cell, wherein the second EPLMN list and the second RPLMNidentifier respectively comprise an EPLMN list and an RPLMN identifierobtained via a most recent circuit switched domain registrationprocedure, and the second access check comprises comparing a PLMNidentifier associated with the CSG cell with the second EPLMN list andthe second RPLMN identifier; and conditioning reporting of the CSG cellbased on the first access check and the second access check.
 2. A methodas defined in claim 1 wherein the first EPLMN list and the first RPLMNidentifier respectively comprise an EPLMN list and an RPLMN identifierobtained via a most recent packet switched domain registrationprocedure, and the first access check comprises comparing a public landmobile network (PLMN) identifier associated with the CSG cell with thefirst EPLMN list and the first RPLMN identifier.
 3. A method as definedin claim 1 wherein conditioning the reporting of the CSG cell based onthe first access check and the second access check comprises: reportingthe CSG cell if at least one of the first access check indicates thatthe mobile station is allowed to access the CSG cell or the secondaccess check indicates that the mobile station is allowed to access theCSG cell; and not reporting the CSG cell if the first access checkindicates that the mobile station is not allowed to access the CSG celland the second access check indicates that the mobile station is notallowed to access the CSG cell.
 4. A method as defined in claim 3further comprising sending information to identify which of the firstaccess check and the second access check indicated that the mobilestation is allowed to access the CSG cell.
 5. A method as defined inclaim 1 wherein conditioning the reporting of the CSG cell based on thefirst access check and the second access check comprises: reporting theCSG cell if the first access check indicates that the mobile station isallowed to access the CSG cell and the second access check indicatesthat the mobile station is allowed to access the CSG cell; and notreporting the CSG cell if at least one of the first access checkindicates that the mobile station is not allowed to access the CSG cellor the second access check indicates that the mobile station is notallowed to access the CSG cell.
 6. A non-transitory machine readablestorage medium comprising machine readable instructions which, whenexecuted, cause a machine to perform the method defined in claim
 1. 7. Amobile station comprising: memory to store machine readableinstructions; and a processor to execute the machine readableinstructions to: store a second equivalent public land mobile network(EPLMN) list and a second RPLMN identifier before obtaining a firstEPLMN list and a first registered public land mobile network (RPLMN)identifier via a subsequent packet switched domain registrationprocedure; perform a first access check based on the first EPLMN listand the first RPLMN identifier to determine whether the mobile stationis allowed to access a closed subscriber group (CSG) cell; perform asecond access check based on a second EPLMN list and a second RPLMNidentifier to determine whether the mobile station is allowed to accessthe CSG cell, wherein the second EPLMN list and the second RPLMNidentifier respectively comprise an EPLMN list and an RPLMN identifierobtained via a most recent circuit switched domain registrationprocedure, and the second access check comprises comparing a PLMNidentifier associated with the CSG cell with the second EPLMN list andthe second RPLMN identifier; and condition reporting of the CSG cellbased on the first access check and the second access check.
 8. A mobilestation as defined in claim 7 wherein the first EPLMN list and the firstRPLMN identifier respectively comprise an EPLMN list and an RPLMNidentifier obtained via a most recent packet switched domainregistration procedure, and to perform the first access check, theprocessor is to compare a public land mobile network (PLMN) identifierassociated with the CSG cell with the first EPLMN list and the firstRPLMN identifier.
 9. A mobile station as defined in claim 7 wherein theprocessor further is to: report the CSG cell if at least one of thefirst access check indicates that the mobile station is allowed toaccess the CSG cell or the second access check indicates that the mobilestation is allowed to access the CSG cell; and not report the CSG cellif the first access check indicates that the mobile station is notallowed to access the CSG cell and the second access check indicatesthat the mobile station is not allowed to access the CSG cell.
 10. Amobile station as defined in claim 9 wherein the processor further is tosend information to identify which of the first access check and thesecond access check indicated that the mobile station is allowed toaccess the CSG cell.
 11. A mobile station as defined in claim 7 whereinthe processor further is to: report the CSG cell if the first accesscheck indicates that the mobile station is allowed to access the CSGcell and the second access check indicates that the mobile station isallowed to access the CSG cell; and not report the CSG cell if at leastone of the first access check indicates that the mobile station is notallowed to access the CSG cell or the second access check indicates thatthe mobile station is not allowed to access the CSG cell.